Sadly the article doesn't really touch on whether or not DMARC accomplishes anything truly useful. When I enabled DMARC for ingress email on one of my own mail servers, it ultimately ended up regularly blocking a handful emails from customers, yet virtually all the spam coming in had valid SPF / DKIM / DMARC, as do most of the phishing attacks.
The core problem is that the real need of email end users need is a way of determining whether or not to trust a given sender. Signatures are purely a technical measure which provides no information on the trustworthiness of the sender. The end result is that email scoring still has to be content based, and the signature check technologies are pure noise with no useful signal for the purpose of determining if an email should actually show up in my inbox.
The tech industry has a bad habit of providing solutions to problems adjacent to problems the user actually needs solved while leaving the user's actual problem unresolved.
Can we use DMARC to ask Gmail to close registrations? Google Calendar to allow far fewer people the ability to send invite notifications? Firebase to close registrations? Azure? Microsoft 365? AWS SES?
It feels like the biggest spammers have swung back to just abusing SaaS and getting SPF / DKIM / DMARC for free from one of the big email providers.
Exactly this. Spammers have the technical competence to overcome any technical hurdle, so using evidence of technical competence achieves nothing.
If it were possible to charge $0.25/email for delivery, I'd be more than happy . However, I'm sure large tech firms will need to say that is "too hard to implement at scale".
Stamp costs don't stop snail mail spam, either, unfortunately. I would be concerned if we added something like bitcoin fees to email delivery rather than curtail spam it would just further encourage grifters seeking ROI on their spam deliveries.
The primary purpose of DMARC is to prevent impersonation not to prevent spam. I own a domain, I implement DMARC to make sure others know when email from my domain is legitimately from my domain.
Then you don't deal with email in the real world. DMARC prevents legitimate emails from people in the real world from being delivered because people make mistakes with their email systems. Passing DMARC is not a signal that the email isn't legitimate; it's merely a sign that someone correctly set up their mail server to modern standards. The email might be an impersonation, or not. There's no way to know.
DMARC does absolutely nothing to prevent the kind of impersonation that occurs in the real world. It doesn't block homoglyphs or or typo-squatting or all the other forms impersonation that matter. It has failed at preventing impersonation.
Just a few days ago I had a phishing email from an elderly woman I had previously done some work for. The message passed DMARC and everything else, and the domain it was sent from was valid. But it was not legitimate; it was an impersonation of her which became obvious once the content was read.
DMARC is noise, not signal. It has to be ignored in the real world as it provides virtually no value beyond blocking emails pretty randomly because someone made a mistake when rotating their DKIM keys or one of a million other mistakes that do happen.
Yes and no. DKIM signs part of the envelope to help recipients detect alteration (by verifying authenticity), SPF locks down the permissible origins for the sender. SPF is in itself imperfect and can in some situations be exploited on open-access shared systems. If the two are used in concert they offer decent protection.
Using both has to be done very carefully, because a positive result from the weaker one (SPF) will override a negative result from the stronger one (DKIM). You should maximally use DKIM and minimally use SPF. Ideally, you should not use SPF at all, but there are some senders that still don't support DKIM.
Many email providers and third party security tools default settings automatically bounce or block SPF failures, no matter what DKIM says... so no, not using SPF completely is a bad idea.
Using it minimally is correct, thou. Route outbound mail through as few controlled relays as possible so your SPF record only needs to list infrastructure you actually *own*, rather than growing it every time a new tool needs to send mail.
I have seen way too many clients almost hit the char limit in a TXT record
SPF failures overriding DKIM successes is a direct violation of RFC 7489 section 4.2 [1]. I have never observed such behavior in the wild, though my experience may be more limited than yours. There are two possible explanations anyway, one is that the DMARC record was missing or misconfigured, the other is that the DKIM check did not actually succeed even though you had reason to believe it should have (e.g., misaligned sender domain, invalid/stale/rotated key, etc.).
I would certainly agree that DKIM is harder to get right. However, the TXT record data size limit is surmountable. You can either use EC algorithms, which have much shorter keys, or stick with e.g. RSA and its very long keys, but span them across multiple 255-byte record data chunks. That having been said, I still think DNS providers should do more to make configuring DKIM easier.
Ultimately, if you have SPF and DKIM set up such that both cover all senders, then you are just using SPF. It is the simpler and more forgiving mechanism, so its broad-scoped successes will always swallow DKIM in practice. The only reason I can think of to do this anyway is if you suspect your email provider will change IPs on you and they don't provide their own SPF record, but if that were the case, they are basically telling you not to use SPF in the first place.
EDIT: RFC 7489 was superseded by RFCs 9989-9901 rather recently. Nevertheless, the definition of success, now given in RFC 9989 section 5.3.5 [2], remains the same.
The "logical OR" of DMARC is absolutely a glaring caveat. I run my own MX and would personally under no circumstance omit SPF, because I consider neither SPF nor DKIM complicated enough to warrant consideration.
This is true, and yet DMARC v1 does not require you to use them in concert. Either one (a valid DKIM-signed message with sender alignment or a message that passes SPF checks with sender alignment) is enough to pass DMARC.
> The tech industry has a bad habit of providing solutions to problems adjacent to problems the user actually needs solved while leaving the user's actual problem unresolved.
My work email is Outlook, which is horribly broken and terrible to use. I have a rule configured to "re-send" all my mail to a different account where I read it with a usable MUA. Unfortunately this seems to break DMARC for external mail as now an email from e.g. user@example.com appears to have been sent by outlook.com.
I'm not familiar with Outlook's resending, but the use case is supported if the sender uses DKIM. If the email is forwarded without changing any details, it can keep the DKIM signature. That allows the forwarded email to still pass DMARC.
Now if the sender used SPF + DMARC but not DKIM, this does not work, since the sender IP can't be verified with the forwarded email. In that case, the forwarder has to change the from address to prevent the email from failing DMARC and be rejected.
In practice, senders using SPF+DMARC but not DKIM should be quite rare, you see DKIM+DMARC much more often.
I have a long-standing email address that forwards to an email system that I run. The operator of the forwarder switched to using Microsoft's mail infrastructure some years ago and the quality of service of the forward has degraded dramatically ever since.
I've often seen messages resent by Microsoft's mail infrastructure with gratuitously broken DKIM signatures, generally due to changes to whitespace that are not anticipated by DKIM's message canonicalization.
I've also seen messages sent by my bank directly to the email system I administer that had broken DKIM signatures apparently due to some sort of antivirus software they had downstream of the DKIM signer.
I never understood the point of the anti-virus adding a message to _outgoing_ emails. Basically "I swear there is no virus in this email I'm sending you, trust me bro".
My domain is very low traffic but, I just looked through my admin email account and opendmarc has rejected 18 attempts by spammers just this past week. More were rejected by my domain's DMARC policy.
It works at small scale when you self-select for technical competency. It does not work at larger scale when that self selection is no longer possible.
My scale is that I ran an ISP for ~500 users before the network was disassembled last month. At that scale, you will encounter people that make mistakes with their email setups. When the people who make mistakes are customers which DMARC prevents delivery of emails, it is an issue as those are exactly the people for which I want to see the emails from.
I get more spam with valid SPF and DKIM via Google's own mail servers than DMARC blocks.
It says something when even gmail doesn't use DMARC as a signal that an email is valid, as gmail regularly blocks legitimate mailing list emails with completely valid signatures and non-spam content from a reputationaly sound IP.
The problem DMARC was supposed to solve (impersonation to reduce spam) isn't solved by DMARC.
Additionally, I would probably guess correctly that almost all spam comes from rotating ASNs these days. Aka from companies that do "growth marketing" or other bullshit that isn't a valid business but just... spamming people.
A lot of the domains that fall through the cracks for single-spam-campaigns have been taken over by botnet campaigns, so the actual owners of said domains probably don't know that their website is spamming everyone else.
But the major providers are the culprit, too, here. Gmail, hotmail, microsoft o365, mailgun ... they all don't even enforce SSL from server to server, and let through "sendmail" like spam because the spammers are paying customers to them.
Source: I am maintaining antispam [1] which I am using to combat spam, phishing, and malware campaigns targeting my customer networks.
I mind email for a number of small orgs (<1000 recipients each). There are so many SPF and DKIM failures from senders who you'd think would know better (Fortune 100-type companies). I don't want complaints from users missing messages so I end up disregarding failures even when published policy says to do otherwise.
I take the opposite approach, I refuse to whitelist domains. When someone internal complains I send a notice to their contact on the other end (CCing the internal recipient) saying their email is misconfigured and ask them to put me in touch with their IT department to help them fix it. I use a script to do some DNS lookups and write the email for me. I have about a 50% success rate getting them to fix it.
My spirit was broken for that kind of work a long time ago.
More often than not I end up talking to someone in the sender's IT who fancies themself an expert and is completely incredulous that there could possibly be a problem on their side ("But we don't have problems sending email to anybody but you...")
I should want to fight the good fight, but it's so demoralizing.
Edit:
Dealing with other IT people on problems like this taught me a ton of humility. It wasn't until I was in my early 30s before I'd reached a level of maturity to approach trouble reports like this being reported to me with an open mind. Before that I fancied myself and expert and, likely, was insufferable in many contexts.
I use postfix and the recipient_access file to control email to my domains which use little email, so the domains are able to process standard email:
admin@example.com OK
postmaster@example.com OK
abuse@example.com OK
webmaster@example.com OK
hostmaster@example.com OK
info@example.com OK
example.com REJECT example.com
The article speaks about DMARC monitoring, but not about "writing" it. So many orgs are too small to have someone paying attention of these things. Where I work, the CTO used to manage the DNS, but with very little understanding of what it all means. It was just copy and paste. And yes, it also says p=none. Probably because it was in the example. It's like setting up a website for your company, and picking some wordpress instance: how are you supposed to know the risks? It's just too much.
LLMs are very good at helping you manage DMARC/DNS related configuration, even as a non-expert. I used it to develop custom DMARC report processing app that: 1. sucks in reports sent to our dmarc inbox into a sqlite db, 2. displays the results in a web page. The reports queue up in the mailbox and I open and start the app once a month to check the status. The agent also also reviewed the state of email-related DNS records, describe what needs to change, including how and why, and verify changes after the fact to ensure they are correct.
Some changes I made at the direction of an agent: fix domainkeys CNAMEs for M365, rotate M365 dkim keys that haven't been rotated for over a decade, fix broken spf record formatting.
My biggest issue is that squarespace refuses to enable dkim signing for transactional emails that they send for us (order/shipping confirmation etc). The email sending service they use (socketlabs) supports it but they are not interested in enabling the feature, so I can't lock down our dmarc. I guess that means squarespace is not a good fit for our needs; it's just disappointing that we have to move to a different platform again for technical reasons that are solvable with a dashboard switch.
Sounds nice, but it adds to the load. Small businesses consider their direct customers much more important, and have little time for this kind of thing. Managing a domain is more work than godaddy makes you believe...
Email has been turned into a by-the-corporation, for-the-corporation service. Corporations need DMARC so they can control email and the ability to spam. The spam I cannot block is spam from Google.
If you decide to think about this, you will quickly realize that email is f*ked and needs to be forked. Perhaps we need a Community Email Initiative that blocks corporations and only allows Community members.
Trust is the one thing you can't buy on the Corporate Internet.
I am sure many people will be offended and down vote this comment because they cannot conceptualize an internet without Corporations.
You can do this right now, and you don't even need to fork anything. E-mail is an internet scale protocol that's not owned or ownable, except by convention. Since you specifically want to cut out Google, and their attempts to capture E-mail are what makes rolling your own E-mail hard anyway, just go for it.
Depending on how hard you want to make it, you can slap all the parts together yourself or use something like Zimbra, Mailcow, iRedMail, mail-in-a-box.
The advantage over a fork, whatever specifically that means, is any service that needs E-mail as an identity verification, still works.
What I am proposing is that community email servers can talk to each other. I have email servers setup - all the hoops - for my community. I want others to set up community servers and be able to interoperate. My server can send and receive from other communities. No corporations, no tracking. If your sever spams it gets dropped from the federation.
Yes it is more complex, and there will be problems and issues. But hey, if we can have crypto currency why can't we get emails?
Yes, email is just completely broken. It's not private, sender identification is mediocre at best (and nonexistent without things like DMARC and SPF), and all the kludges thrown up make self-hosting harder. Spam has zero cost basically also. Nobody trusts email anymore for anything confidential, it's become a clumsy notification service "come check our portal for your real email".
It's time for a new protocol with end to end encryption and sender verification built-in. That shouldn't be as hard as it sounds, because at the time when email was invented the internet was very different. Connections were intermittent, for example I would retrieve my email once a day with UUCP (and some other people would use batched-SMTP). Which means you could not rely on the sending and receiving server being able to communicate directly. In this day and age this is possible and that direct communication opens up a lot of better crypto like key generation algorithms which require both parties to be online at the same time.
The problem is, is you don't allow corpos you will break 95% of mainstream people's usecases. So I think this is a non-starter, unfortunately, though it is a lofty goal.
You can already do this without changing anything. Just set your corporate mailserver to not accept mail from common community email providers. There's a reason nobody does this, and it's because it's a bad idea.
There is so much crossover between personal email and corporate email.
My previous employer did this, and no one seemed to miss it. If you had a use case to add an exception (the most common was to send yourself a mail from your personal Gmail, to print something on the corporate printers) that was supported and straightforward too.
No, email is the only digital communication left where I can talk to normie relatives AND businesses without having an account on normie tech service. DMARC does not impede that at all and it not a valid cause to throw away this lucky artifact of computing history.
I really think we should be solving a much bigger problem of the major email providers not providing an automated way of handling abuse and not caring about abuse reports at all. Most of my spam comes from the three major email providers and at this point I gave up even trying to send abuse reports because they just get ignored.
The big companies do not have to care because nobody will block Google, Microsoft or Amazon. They are too big to fail.
Spoofing a From field is an insignificant problem in comparison.
It's ironic that I set everything up correctly on my self hosted domain and still end up in spam because of my low volume.
I even go to the trouble of registering in their Postmaster Tools and clogging up my DNS with their verification tokens all for the tools to tell me I don't send enough mail while they happily pass what little mail I send straight to spam.
Not enough outgoing email
You haven't sent enough email to personal Gmail (@gmail.com) accounts to determine deliverability status for your domain and messages.
Each screen only shows: "No data was found for this domain."
Guess it doesn't help that as I look today the Postmaster Tools dashboard shows "Last updated Sun, Apr 26, at 9:30 AM."
Then on the other hand Google can flood me with spam filled Google Calendar Invites and Google Drive Share notifications, all fully DKIM signed because they are coming out of those services, all day long.
Microsoft have also recently changed their Smart Network Data Service (SNDS) so now only my cloud provider can access the console as they only allow verification to the owner of the whole ASN block you're under. I can't access detail about my domain anymore, and still my mail goes to junk. Unless you own a chunk of IPv4 ASN range you're out of luck. IPv6? Nope, not at Microsoft. "Please note that IPv6 is not currently supported." [1]
In the same boat here. At least still have a good standing at Microft. Lost goodwill at big G by what I vaguely narrowed down to self hosted images in e-mail signature.
Don't self-hosted images in the email signature allow you to track whether the email was opened or not and potentially where it was opened? I can only imagine they want you to pay for that privilege as a service.
Gmail already proxies embedded images so you'd only be able to track when an email was opened the first time. Anyway, I have been sending (very low volume) of mails with self-hosted images embedded in the body for years without problems with Gmail but Microsoft doesn't like my VPS IP because sometimes there are temporarly bad actors on the same block. So I guess it's mostly random luck.
I have set up DMARC, SPF, DKIM and whatnot. Sadly no one seems to take this as a signal for a competent mail setup, so Microsoft's mail servers regularly block my mails because of the surrounding IP range reputation - not because any spam would originate from my IPs or domains.
I am running email server for my private domain using https://github.com/docker-mailserver/docker-mailserver . One day in 2023 i decided that beside of dkim i maybe should also enable dmarc. Because ... well, why not. What happened was that i started reciving regular reports over email from ms and google containing compressed xml containing no info other that empty report was generated. What should I do with that? At that time i could not find any tool that would be able to extract valuable info from that, so I disabled dmarc. Havent looked back since.
There are lots of free tools that automatically analyze the reports for you (you send it to them, instead of yourself).
But if you send all emails for your domain from one email server, you could just disable rua reporting. The reports are mainly useful to see whether you have some misconfigired email server somewhere that causes (or will cause) dropped emails. That can easily happen if you send some email from your own server, some via sendgrid, some via some marketing tool, and start to lose track of them. But for a personal email server, that's not common.
The reports are kind of useful when first enabling, if you want to get warnings about non-compliant mail, but after you're established, they're not really useful, so you should turn reports off, but you can do that without turning off the whole thing.
I didn't see it explicitly mentioned in the post, I wonder if they filtered exclusively for domains with mx records. Because I would assume that lots of domains just don't have email configured and therefore aren't aware that you should still setup DMARC to prevent impersination of your domain.
DMARC, just like SPF before it, solves nothing. The spammers adapt. And unlike SPF, DMARC has an enormous technology surface area. Its failure modes are legion, and each one is tedious to run down to resolution. Which just returns you to something which never pays the rent anyway.
I’d be interested these stats broken down between domains associated with operating companies and personal or hobby domains.
The latter are likely to adopt much more slowly simply because of less perceived risk, lower payoff (no vendor reviews), and less dedicated technical expertise.
Just like personal sites were slow to adopt HTTPS. Mass HTTPS adoption happened once browser warnings and SEO incentives rendered sites mostly useless without it.
I'd expect the opposite really. Personal domains sending email are more likely to be run by MTA enthusiasts who don't have any money riding on others being able to receive their mails compared to corporate IT where mail is just one more thing they have to wrangle and really don't need the company leadership being angry at them because the spam-as-a-service company that marketing has been using without telling anyone gets blocked due to their DNS settings.
Article is missing a note on the existence of MX records for the domains. Sure, you can easily have a send-only domain without an MX record, but the common case is likely to setup both send and receive capability. It would be interesting to have that number included as domains without MX and DMARC might just not be configured for email at all. Worst case the 45% of domains without DMARC are simply not relevant for email and thus not configured at all. I would find "x% of domains with configured email don't enforce DMARC" more interesting.
I am self-hosting my (secondary) email and have only implemented SPF and DKIM. This works fine on a practical level for me. What would be the benefit of setting up DMARC on top?
DMARC is essentially an opt-in to strict mode. Primarily it prevents other people from forging email to look like it is coming from you. The goal of dmarc is to prevent other people from impersonating you.
Google, Microsoft, Amazon and others send me summary reports of people spoofing my domains. I have dmarc set for them to accept the email, mark it spam (presumably) and send me a report. I really should and can tell them to reject the spam completely - another setting in dmarc but haven't yet out of laziness basically.
`p=reject`, ESPECIALLY for your personal email. `p=quarantine` is really only useful if you suspect your marketing department has set up some email blaster somewhere.
Realistically spoofed address (unauthenticated email) will be treated as spam and it’ll be implicitly quarantined or rejected as such by many well-known mail receivers. You can make this an explicit “reject” by publishing DMARC policy for your domain.
For example, gmail.com treats unauthenticated email as spam implicitly, regardless of DMARC policy.
SPF allows to say “these IPs are authorised to send emails as example.com”, where DMARC allows to say “I as domain owner recommend to quarantine emails that fail SPF and DKIM”, it also allows finer alignment (ie, matching between different “from” parameters) configuration and reporting by the receivers.
Of course, with absence of DNARC policies, receivers default to some internal defaults, or may ignore the policies altogether. But at least, the big ones send DMARC reports.
MAIL FROM: foo@example.net
RCPT TO: victim@example.com
DATA
From: service@paypal.co.uk
To: victim@example.com
Subject: We are updating our Terms of Service
[...]
SPF checks whether the sending host is allowed to send e-mail from example.net (the envelope sender).
The recipient sees service@paypal.co.uk (the From address on the inner message), because most ESPs do them the great disservice of not indicating that the sender identities are not aligned.
Adding a DMARC record to a domain requires that e-mail whose inner messages claim to be from that domain must have sender alignment to the envelope sender.
The above message would pass SPF (if the spammer owns example.net and has created SPF records for themselves) but would fail DMARC (paypal.co.uk's DMARC record exists, so alignment is required, and yet example.net != paypal.co.uk, so they are not aligned). In this case their DMARC policy says to reject the message, so (if the recipient is checking DMARC) it would either be rejected outright or it would land in Spam/Quarantine rather than Inbox.
Not always. An email has a valid SPF when its return path email’s domain permits the sending server’s IP. But that email may have a forged From: header (which causes an SPF mis-alignment), and the receiving server checks the DMARC of *the From header* domain to determine how to handle that mis-alignment.
> What would be the benefit of setting up DMARC on top?
Some mail providers will junk your mail if you don't have a reject/quarantine DMARC policy because you're seen as enabling the spammers so everything out of your domain must be punished.
The biggest benefit I saw in a small domain was greatly reduced backscatter spam. Before someone’d randomly make up a billion emails on my domain and send “from” them, and I’d get various out of office replies, etc (catch all) - that basically never happens anymore.
DMARC is simple in theory but quite tricky in practice (with subdomains, for example).
You follow the guide for a service (say Mailgun, for example) and everything looks fine, but CloudFlare shows up issues. You fix those issues and you're conflicting the mail service guide.
Anyways, the new CF AI tool is relatively decent for this purpose, explains the fact that most warnings in CF are harmless, but the lack of standardized guidelines is annoying to say the least.
Sadly the article doesn't really touch on whether or not DMARC accomplishes anything truly useful. When I enabled DMARC for ingress email on one of my own mail servers, it ultimately ended up regularly blocking a handful emails from customers, yet virtually all the spam coming in had valid SPF / DKIM / DMARC, as do most of the phishing attacks.
The core problem is that the real need of email end users need is a way of determining whether or not to trust a given sender. Signatures are purely a technical measure which provides no information on the trustworthiness of the sender. The end result is that email scoring still has to be content based, and the signature check technologies are pure noise with no useful signal for the purpose of determining if an email should actually show up in my inbox.
The tech industry has a bad habit of providing solutions to problems adjacent to problems the user actually needs solved while leaving the user's actual problem unresolved.
> The core problem is that the real need of email end users need is a way of determining whether or not to trust a given sender.
Which is only the core problem because dmarc fixed the other core problem of figuring out who the given sender is.
DMARC does not solve everything, but it does make other solutions more effective.
> virtually all the spam coming in had valid SPF / DKIM / DMARC, as do most of the phishing attacks.
This should create a means to go after the domain owners via registrar and trail of ownership, even so far as blocking email from the domain.
Forcing the spammers to pass DMARC creates a burden and an evidence trail that didn't exist before.
Can we use DMARC to ask Gmail to close registrations? Google Calendar to allow far fewer people the ability to send invite notifications? Firebase to close registrations? Azure? Microsoft 365? AWS SES?
It feels like the biggest spammers have swung back to just abusing SaaS and getting SPF / DKIM / DMARC for free from one of the big email providers.
Exactly this. Spammers have the technical competence to overcome any technical hurdle, so using evidence of technical competence achieves nothing.
If it were possible to charge $0.25/email for delivery, I'd be more than happy . However, I'm sure large tech firms will need to say that is "too hard to implement at scale".
Stamp costs don't stop snail mail spam, either, unfortunately. I would be concerned if we added something like bitcoin fees to email delivery rather than curtail spam it would just further encourage grifters seeking ROI on their spam deliveries.
What spammers are using the same domain for longer than couple of hours?
What do you expect to achieve by blocking an already abandoned domain?
They're generally hosted on a google or microsoft 365 or something slightly less shady. Good luck with that.
The primary purpose of DMARC is to prevent impersonation not to prevent spam. I own a domain, I implement DMARC to make sure others know when email from my domain is legitimately from my domain.
Then you don't deal with email in the real world. DMARC prevents legitimate emails from people in the real world from being delivered because people make mistakes with their email systems. Passing DMARC is not a signal that the email isn't legitimate; it's merely a sign that someone correctly set up their mail server to modern standards. The email might be an impersonation, or not. There's no way to know.
DMARC does absolutely nothing to prevent the kind of impersonation that occurs in the real world. It doesn't block homoglyphs or or typo-squatting or all the other forms impersonation that matter. It has failed at preventing impersonation.
Just a few days ago I had a phishing email from an elderly woman I had previously done some work for. The message passed DMARC and everything else, and the domain it was sent from was valid. But it was not legitimate; it was an impersonation of her which became obvious once the content was read.
DMARC is noise, not signal. It has to be ignored in the real world as it provides virtually no value beyond blocking emails pretty randomly because someone made a mistake when rotating their DKIM keys or one of a million other mistakes that do happen.
Okay but that doesn’t detract from the intended purpose of DMARC.
Isn't that the purpose of DKIM and SPF already?
DKIM and SPF validate a message. DMARC sets a policy as to what to do with it (quarantine/reject.)
ELI5: https://www.reddit.com/r/sysadmin/comments/16gvtdj/comment/k...
Yes and no. DKIM signs part of the envelope to help recipients detect alteration (by verifying authenticity), SPF locks down the permissible origins for the sender. SPF is in itself imperfect and can in some situations be exploited on open-access shared systems. If the two are used in concert they offer decent protection.
Using both has to be done very carefully, because a positive result from the weaker one (SPF) will override a negative result from the stronger one (DKIM). You should maximally use DKIM and minimally use SPF. Ideally, you should not use SPF at all, but there are some senders that still don't support DKIM.
Many email providers and third party security tools default settings automatically bounce or block SPF failures, no matter what DKIM says... so no, not using SPF completely is a bad idea.
Using it minimally is correct, thou. Route outbound mail through as few controlled relays as possible so your SPF record only needs to list infrastructure you actually *own*, rather than growing it every time a new tool needs to send mail.
I have seen way too many clients almost hit the char limit in a TXT record
SPF failures overriding DKIM successes is a direct violation of RFC 7489 section 4.2 [1]. I have never observed such behavior in the wild, though my experience may be more limited than yours. There are two possible explanations anyway, one is that the DMARC record was missing or misconfigured, the other is that the DKIM check did not actually succeed even though you had reason to believe it should have (e.g., misaligned sender domain, invalid/stale/rotated key, etc.).
I would certainly agree that DKIM is harder to get right. However, the TXT record data size limit is surmountable. You can either use EC algorithms, which have much shorter keys, or stick with e.g. RSA and its very long keys, but span them across multiple 255-byte record data chunks. That having been said, I still think DNS providers should do more to make configuring DKIM easier.
Ultimately, if you have SPF and DKIM set up such that both cover all senders, then you are just using SPF. It is the simpler and more forgiving mechanism, so its broad-scoped successes will always swallow DKIM in practice. The only reason I can think of to do this anyway is if you suspect your email provider will change IPs on you and they don't provide their own SPF record, but if that were the case, they are basically telling you not to use SPF in the first place.
EDIT: RFC 7489 was superseded by RFCs 9989-9901 rather recently. Nevertheless, the definition of success, now given in RFC 9989 section 5.3.5 [2], remains the same.
[1] = https://datatracker.ietf.org/doc/html/rfc7489#section-4.2
[2] = https://datatracker.ietf.org/doc/html/rfc9989#section-5.3.5
The "logical OR" of DMARC is absolutely a glaring caveat. I run my own MX and would personally under no circumstance omit SPF, because I consider neither SPF nor DKIM complicated enough to warrant consideration.
This is true, and yet DMARC v1 does not require you to use them in concert. Either one (a valid DKIM-signed message with sender alignment or a message that passes SPF checks with sender alignment) is enough to pass DMARC.
> The tech industry has a bad habit of providing solutions to problems adjacent to problems the user actually needs solved while leaving the user's actual problem unresolved.
Extremely well said.
My work email is Outlook, which is horribly broken and terrible to use. I have a rule configured to "re-send" all my mail to a different account where I read it with a usable MUA. Unfortunately this seems to break DMARC for external mail as now an email from e.g. user@example.com appears to have been sent by outlook.com.
I'm not familiar with Outlook's resending, but the use case is supported if the sender uses DKIM. If the email is forwarded without changing any details, it can keep the DKIM signature. That allows the forwarded email to still pass DMARC.
Now if the sender used SPF + DMARC but not DKIM, this does not work, since the sender IP can't be verified with the forwarded email. In that case, the forwarder has to change the from address to prevent the email from failing DMARC and be rejected.
In practice, senders using SPF+DMARC but not DKIM should be quite rare, you see DKIM+DMARC much more often.
I have a long-standing email address that forwards to an email system that I run. The operator of the forwarder switched to using Microsoft's mail infrastructure some years ago and the quality of service of the forward has degraded dramatically ever since.
I've often seen messages resent by Microsoft's mail infrastructure with gratuitously broken DKIM signatures, generally due to changes to whitespace that are not anticipated by DKIM's message canonicalization.
I've also seen messages sent by my bank directly to the email system I administer that had broken DKIM signatures apparently due to some sort of antivirus software they had downstream of the DKIM signer.
Outlook.com also seems to routinely ignore DMARC (it will bounce emails with a DMARC that's report only)
I never understood the point of the anti-virus adding a message to _outgoing_ emails. Basically "I swear there is no virus in this email I'm sending you, trust me bro".
"We take security seriously."
My domain is very low traffic but, I just looked through my admin email account and opendmarc has rejected 18 attempts by spammers just this past week. More were rejected by my domain's DMARC policy.
It works at small scale when you self-select for technical competency. It does not work at larger scale when that self selection is no longer possible.
My scale is that I ran an ISP for ~500 users before the network was disassembled last month. At that scale, you will encounter people that make mistakes with their email setups. When the people who make mistakes are customers which DMARC prevents delivery of emails, it is an issue as those are exactly the people for which I want to see the emails from.
I get more spam with valid SPF and DKIM via Google's own mail servers than DMARC blocks.
It says something when even gmail doesn't use DMARC as a signal that an email is valid, as gmail regularly blocks legitimate mailing list emails with completely valid signatures and non-spam content from a reputationaly sound IP.
The problem DMARC was supposed to solve (impersonation to reduce spam) isn't solved by DMARC.
^ this
Additionally, I would probably guess correctly that almost all spam comes from rotating ASNs these days. Aka from companies that do "growth marketing" or other bullshit that isn't a valid business but just... spamming people.
A lot of the domains that fall through the cracks for single-spam-campaigns have been taken over by botnet campaigns, so the actual owners of said domains probably don't know that their website is spamming everyone else.
But the major providers are the culprit, too, here. Gmail, hotmail, microsoft o365, mailgun ... they all don't even enforce SSL from server to server, and let through "sendmail" like spam because the spammers are paying customers to them.
Source: I am maintaining antispam [1] which I am using to combat spam, phishing, and malware campaigns targeting my customer networks.
[1] https://github.com/cookiengineer/antispam
I mind email for a number of small orgs (<1000 recipients each). There are so many SPF and DKIM failures from senders who you'd think would know better (Fortune 100-type companies). I don't want complaints from users missing messages so I end up disregarding failures even when published policy says to do otherwise.
I take the opposite approach, I refuse to whitelist domains. When someone internal complains I send a notice to their contact on the other end (CCing the internal recipient) saying their email is misconfigured and ask them to put me in touch with their IT department to help them fix it. I use a script to do some DNS lookups and write the email for me. I have about a 50% success rate getting them to fix it.
My spirit was broken for that kind of work a long time ago.
More often than not I end up talking to someone in the sender's IT who fancies themself an expert and is completely incredulous that there could possibly be a problem on their side ("But we don't have problems sending email to anybody but you...")
I should want to fight the good fight, but it's so demoralizing.
Edit:
Dealing with other IT people on problems like this taught me a ton of humility. It wasn't until I was in my early 30s before I'd reached a level of maturity to approach trouble reports like this being reported to me with an open mind. Before that I fancied myself and expert and, likely, was insufferable in many contexts.
Now I'm insufferable in fewer contexts.
What happens in the other 50%? Your users work around you somehow?
I have also done this, but instead by finding someone from IT or security on LinkedIn and messaging them there.
If you have any domains that does not use email, it may be a good idea to set up some DNS records to prevent it being used.
DNS SPF record: mydomain.io. TXT "v=spf1 -all"
DNS DMARC: _dmarc.mydomain.io. TXT "v=DMARC1; p=reject; sp=reject; adkim=s; aspf=s"
That ought to stop anyone trying to use your domains as source.
Yes! IMHO every registrar should be turning this on by default. Every DNS should do this by default until the owner explicitly turns on email sending.
It would solve a lot of issues globally.
Also consider (using your example domain):
to restrict SPF on all subdomains.I use postfix and the recipient_access file to control email to my domains which use little email, so the domains are able to process standard email:
admin@example.com OK postmaster@example.com OK abuse@example.com OK webmaster@example.com OK hostmaster@example.com OK info@example.com OK example.com REJECT example.com
The article speaks about DMARC monitoring, but not about "writing" it. So many orgs are too small to have someone paying attention of these things. Where I work, the CTO used to manage the DNS, but with very little understanding of what it all means. It was just copy and paste. And yes, it also says p=none. Probably because it was in the example. It's like setting up a website for your company, and picking some wordpress instance: how are you supposed to know the risks? It's just too much.
LLMs are very good at helping you manage DMARC/DNS related configuration, even as a non-expert. I used it to develop custom DMARC report processing app that: 1. sucks in reports sent to our dmarc inbox into a sqlite db, 2. displays the results in a web page. The reports queue up in the mailbox and I open and start the app once a month to check the status. The agent also also reviewed the state of email-related DNS records, describe what needs to change, including how and why, and verify changes after the fact to ensure they are correct.
Some changes I made at the direction of an agent: fix domainkeys CNAMEs for M365, rotate M365 dkim keys that haven't been rotated for over a decade, fix broken spf record formatting.
My biggest issue is that squarespace refuses to enable dkim signing for transactional emails that they send for us (order/shipping confirmation etc). The email sending service they use (socketlabs) supports it but they are not interested in enabling the feature, so I can't lock down our dmarc. I guess that means squarespace is not a good fit for our needs; it's just disappointing that we have to move to a different platform again for technical reasons that are solvable with a dashboard switch.
Sounds nice, but it adds to the load. Small businesses consider their direct customers much more important, and have little time for this kind of thing. Managing a domain is more work than godaddy makes you believe...
Email has been turned into a by-the-corporation, for-the-corporation service. Corporations need DMARC so they can control email and the ability to spam. The spam I cannot block is spam from Google.
If you decide to think about this, you will quickly realize that email is f*ked and needs to be forked. Perhaps we need a Community Email Initiative that blocks corporations and only allows Community members.
Trust is the one thing you can't buy on the Corporate Internet.
I am sure many people will be offended and down vote this comment because they cannot conceptualize an internet without Corporations.
You can do this right now, and you don't even need to fork anything. E-mail is an internet scale protocol that's not owned or ownable, except by convention. Since you specifically want to cut out Google, and their attempts to capture E-mail are what makes rolling your own E-mail hard anyway, just go for it.
Depending on how hard you want to make it, you can slap all the parts together yourself or use something like Zimbra, Mailcow, iRedMail, mail-in-a-box.
The advantage over a fork, whatever specifically that means, is any service that needs E-mail as an identity verification, still works.
What I am proposing is that community email servers can talk to each other. I have email servers setup - all the hoops - for my community. I want others to set up community servers and be able to interoperate. My server can send and receive from other communities. No corporations, no tracking. If your sever spams it gets dropped from the federation. Yes it is more complex, and there will be problems and issues. But hey, if we can have crypto currency why can't we get emails?
Yes, email is just completely broken. It's not private, sender identification is mediocre at best (and nonexistent without things like DMARC and SPF), and all the kludges thrown up make self-hosting harder. Spam has zero cost basically also. Nobody trusts email anymore for anything confidential, it's become a clumsy notification service "come check our portal for your real email".
It's time for a new protocol with end to end encryption and sender verification built-in. That shouldn't be as hard as it sounds, because at the time when email was invented the internet was very different. Connections were intermittent, for example I would retrieve my email once a day with UUCP (and some other people would use batched-SMTP). Which means you could not rely on the sending and receiving server being able to communicate directly. In this day and age this is possible and that direct communication opens up a lot of better crypto like key generation algorithms which require both parties to be online at the same time.
The problem is, is you don't allow corpos you will break 95% of mainstream people's usecases. So I think this is a non-starter, unfortunately, though it is a lofty goal.
You can already do this without changing anything. Just set your corporate mailserver to not accept mail from common community email providers. There's a reason nobody does this, and it's because it's a bad idea.
There is so much crossover between personal email and corporate email.
My previous employer did this, and no one seemed to miss it. If you had a use case to add an exception (the most common was to send yourself a mail from your personal Gmail, to print something on the corporate printers) that was supported and straightforward too.
No, email is the only digital communication left where I can talk to normie relatives AND businesses without having an account on normie tech service. DMARC does not impede that at all and it not a valid cause to throw away this lucky artifact of computing history.
What do you mean “fork”? Just buy a domain and install an email server.
Buy a domain? If you're going to fork email, may as well go the whole hog and fork DNS too!
Have your own gmail.com
The domains that do enforce DMARC are apparently configured so badly that the German secure email provider mailbox.org decided not to honor DMARC.
See this thread in German: https://userforum.mailbox.org/topic/10676-mailbox-org-akzept...
I really think we should be solving a much bigger problem of the major email providers not providing an automated way of handling abuse and not caring about abuse reports at all. Most of my spam comes from the three major email providers and at this point I gave up even trying to send abuse reports because they just get ignored.
The big companies do not have to care because nobody will block Google, Microsoft or Amazon. They are too big to fail.
Spoofing a From field is an insignificant problem in comparison.
It's ironic that I set everything up correctly on my self hosted domain and still end up in spam because of my low volume.
I even go to the trouble of registering in their Postmaster Tools and clogging up my DNS with their verification tokens all for the tools to tell me I don't send enough mail while they happily pass what little mail I send straight to spam.
Each screen only shows: "No data was found for this domain."Guess it doesn't help that as I look today the Postmaster Tools dashboard shows "Last updated Sun, Apr 26, at 9:30 AM."
Then on the other hand Google can flood me with spam filled Google Calendar Invites and Google Drive Share notifications, all fully DKIM signed because they are coming out of those services, all day long.
Microsoft have also recently changed their Smart Network Data Service (SNDS) so now only my cloud provider can access the console as they only allow verification to the owner of the whole ASN block you're under. I can't access detail about my domain anymore, and still my mail goes to junk. Unless you own a chunk of IPv4 ASN range you're out of luck. IPv6? Nope, not at Microsoft. "Please note that IPv6 is not currently supported." [1]
[1]: https://substrate.office.com/ip-domain-management-snds/SNDS/...
I just checked my email server's IP and it is still listed at https://substrate.office.com/ip-domain-management-snds/SNDS/...
And I can Remove or Renew Access, or those links are showing.
In the same boat here. At least still have a good standing at Microft. Lost goodwill at big G by what I vaguely narrowed down to self hosted images in e-mail signature.
Don't self-hosted images in the email signature allow you to track whether the email was opened or not and potentially where it was opened? I can only imagine they want you to pay for that privilege as a service.
Gmail already proxies embedded images so you'd only be able to track when an email was opened the first time. Anyway, I have been sending (very low volume) of mails with self-hosted images embedded in the body for years without problems with Gmail but Microsoft doesn't like my VPS IP because sometimes there are temporarly bad actors on the same block. So I guess it's mostly random luck.
Email providers do have an automated way of handling abuse. Send the message to abuse@provider and they automatically ignore it. =)
Agreed, most spam has valid DMARC - whether that's bigmail.com or just nobodcarestoprotectsubdomains.randompwnedcompany.com
Given how much spam has valid DMARC/DKIM it is just useless.
Turns out making absolutely sure email isn't faked means jack shit if user isn't even looking at it, or the spoofed domains looks "close enough".
Currently the big pile of mail "security" extensions is basically useless pile of waste that just gives mail server admins some extra work.
I have set up DMARC, SPF, DKIM and whatnot. Sadly no one seems to take this as a signal for a competent mail setup, so Microsoft's mail servers regularly block my mails because of the surrounding IP range reputation - not because any spam would originate from my IPs or domains.
I am running email server for my private domain using https://github.com/docker-mailserver/docker-mailserver . One day in 2023 i decided that beside of dkim i maybe should also enable dmarc. Because ... well, why not. What happened was that i started reciving regular reports over email from ms and google containing compressed xml containing no info other that empty report was generated. What should I do with that? At that time i could not find any tool that would be able to extract valuable info from that, so I disabled dmarc. Havent looked back since.
There are lots of free tools that automatically analyze the reports for you (you send it to them, instead of yourself).
But if you send all emails for your domain from one email server, you could just disable rua reporting. The reports are mainly useful to see whether you have some misconfigired email server somewhere that causes (or will cause) dropped emails. That can easily happen if you send some email from your own server, some via sendgrid, some via some marketing tool, and start to lose track of them. But for a personal email server, that's not common.
The reports are kind of useful when first enabling, if you want to get warnings about non-compliant mail, but after you're established, they're not really useful, so you should turn reports off, but you can do that without turning off the whole thing.
I didn't see it explicitly mentioned in the post, I wonder if they filtered exclusively for domains with mx records. Because I would assume that lots of domains just don't have email configured and therefore aren't aware that you should still setup DMARC to prevent impersination of your domain.
I'll set up DMARC after I get DKIM working... migrating my homelab has been taking forever...
DMARC, just like SPF before it, solves nothing. The spammers adapt. And unlike SPF, DMARC has an enormous technology surface area. Its failure modes are legion, and each one is tedious to run down to resolution. Which just returns you to something which never pays the rent anyway.
I’d be interested these stats broken down between domains associated with operating companies and personal or hobby domains.
The latter are likely to adopt much more slowly simply because of less perceived risk, lower payoff (no vendor reviews), and less dedicated technical expertise.
Just like personal sites were slow to adopt HTTPS. Mass HTTPS adoption happened once browser warnings and SEO incentives rendered sites mostly useless without it.
I'd expect the opposite really. Personal domains sending email are more likely to be run by MTA enthusiasts who don't have any money riding on others being able to receive their mails compared to corporate IT where mail is just one more thing they have to wrangle and really don't need the company leadership being angry at them because the spam-as-a-service company that marketing has been using without telling anyone gets blocked due to their DNS settings.
Article is missing a note on the existence of MX records for the domains. Sure, you can easily have a send-only domain without an MX record, but the common case is likely to setup both send and receive capability. It would be interesting to have that number included as domains without MX and DMARC might just not be configured for email at all. Worst case the 45% of domains without DMARC are simply not relevant for email and thus not configured at all. I would find "x% of domains with configured email don't enforce DMARC" more interesting.
Technically you can receive mail without MX records if your mail server is on the same host as the web server.
I am self-hosting my (secondary) email and have only implemented SPF and DKIM. This works fine on a practical level for me. What would be the benefit of setting up DMARC on top?
DMARC is essentially an opt-in to strict mode. Primarily it prevents other people from forging email to look like it is coming from you. The goal of dmarc is to prevent other people from impersonating you.
Because if someone spoofs an email coming from your domain DMARC tells the receiver what to do with the spoofed email.
Google, Microsoft, Amazon and others send me summary reports of people spoofing my domains. I have dmarc set for them to accept the email, mark it spam (presumably) and send me a report. I really should and can tell them to reject the spam completely - another setting in dmarc but haven't yet out of laziness basically.
And what is the sane way to handle a spoofed email?
`p=reject`, ESPECIALLY for your personal email. `p=quarantine` is really only useful if you suspect your marketing department has set up some email blaster somewhere.
Realistically spoofed address (unauthenticated email) will be treated as spam and it’ll be implicitly quarantined or rejected as such by many well-known mail receivers. You can make this an explicit “reject” by publishing DMARC policy for your domain.
For example, gmail.com treats unauthenticated email as spam implicitly, regardless of DMARC policy.
That's what the policy setting tells the recipient. You can tell them to trest it as normal, send it to spam or delete it.
The report that they send you is useful for you to make sure your emails that you expect to go through are going through.
Reject it in the SMTP transaction.
And SPF doesn't?
Technically, no.
SPF allows to say “these IPs are authorised to send emails as example.com”, where DMARC allows to say “I as domain owner recommend to quarantine emails that fail SPF and DKIM”, it also allows finer alignment (ie, matching between different “from” parameters) configuration and reporting by the receivers.
Of course, with absence of DNARC policies, receivers default to some internal defaults, or may ignore the policies altogether. But at least, the big ones send DMARC reports.
No, it doesn't.
In the following SMTP conversation:
SPF checks whether the sending host is allowed to send e-mail from example.net (the envelope sender).The recipient sees service@paypal.co.uk (the From address on the inner message), because most ESPs do them the great disservice of not indicating that the sender identities are not aligned.
Adding a DMARC record to a domain requires that e-mail whose inner messages claim to be from that domain must have sender alignment to the envelope sender.
The above message would pass SPF (if the spammer owns example.net and has created SPF records for themselves) but would fail DMARC (paypal.co.uk's DMARC record exists, so alignment is required, and yet example.net != paypal.co.uk, so they are not aligned). In this case their DMARC policy says to reject the message, so (if the recipient is checking DMARC) it would either be rejected outright or it would land in Spam/Quarantine rather than Inbox.
Not always. An email has a valid SPF when its return path email’s domain permits the sending server’s IP. But that email may have a forged From: header (which causes an SPF mis-alignment), and the receiving server checks the DMARC of *the From header* domain to determine how to handle that mis-alignment.
> What would be the benefit of setting up DMARC on top?
Some mail providers will junk your mail if you don't have a reject/quarantine DMARC policy because you're seen as enabling the spammers so everything out of your domain must be punished.
[citation needed]
When properly configured, particularly at an enforcement policy of p=quarantine or p=reject, DMARC can positively impact inbox placement.
https://mxtoolbox.com/dmarc/details/email-deliverability
The biggest benefit I saw in a small domain was greatly reduced backscatter spam. Before someone’d randomly make up a billion emails on my domain and send “from” them, and I’d get various out of office replies, etc (catch all) - that basically never happens anymore.
Domains with stricter DMARC that isn't on 'none' are in my experience more likely to be spammers than desirable email.
68.4% is actually a lot. Considering how badly abused email has always been, I'm actually surprised its nearly 70% and growing. Cup half full I guess
68.4% still don't enforce it, i.e. adoption is just over 30%, not nearly 70%.
Thank you
You misunderstood, it's 31.6% actually.
Thank you
Using DMARC information is complicated in practice in the real world, by Chris Siebenmann
https://utcc.utoronto.ca/~cks/space/blog/spam/DMARCPractical...
DMARC is simple in theory but quite tricky in practice (with subdomains, for example). You follow the guide for a service (say Mailgun, for example) and everything looks fine, but CloudFlare shows up issues. You fix those issues and you're conflicting the mail service guide.
Anyways, the new CF AI tool is relatively decent for this purpose, explains the fact that most warnings in CF are harmless, but the lack of standardized guidelines is annoying to say the least.