Who's publishing DMARC?

DMARC is a way for a domain owner to say “If you see this domain in a From: header and it’s not been sent straight from us, please don’t deliver the mail”. If a domain is only used for bulk and transactional mail, it can mitigate a subset of phishing attacks without causing too many problems for legitimate email.
In other cases, it can cause significant problems. Some of those problems impact discussion lists, but others cause problems for ESPs servicing small companies and individuals. ESP customers use their email addresses in the From: field; if they’re a small customer using the email address provided by their ISP, and that ISP publishes a DMARC record with p=reject, a large chunk of the mail they’re sending will bounce. When that happens recipients will stop getting their email, they’ll be removed from the mailing list due to bounces, and there’s some risk of blocks being raised against the sending IP address.
Because of that, it’s good to be able to see what consumer ISPs are doing with DMARC.
I’ve created a tool at dmarc.wordtothewise.com that regularly checks a list of large consumer ISPs and webmail providers and sees what DMARC records they’re publishing.
There are two main variants of DMARC records.
One is policy “reject” – meaning that mail that isn’t authenticated (or for which authentication has been broken in transit) will likely be rejected.
The other is policy “none” – meaning that the ISP publishing the record doesn’t want recipients to change their delivery decisions, but are asking for feedback about their mailstream, and how much of it fails authentication. That can mean that the ISP is evaluating whether or not to publish p=REJECT, or is in the process of deploying p=REJECT. Or it can just mean that they’re using DMARC to monitor where mail using their domain in the From: address is being sent from. There’s no way to tell which is the case unless they’ve made an announcement about their plans.
Hopefully this will be a useful tool to monitor DMARC deployment by consumer ISPs, and to help diagnose delivery problems that may be caused by DMARC.

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DMARC and organizations

Comcast recently published a statement on DMARC over on their postmaster page. The short version is that Comcast is publishing a DMARC record, but has no current intentions to publish a p=reject policy for Comcast user email. Comcast will be publishing a p=reject for some of their domains that they use exclusively to communicate with customers, like billing notices and security notices.
Comcast does point out that Yahoo! and AOL’s usage of p=reject is “not common usage.”
This is something a lot of people have been arguing loudly about on various mail operations lists and network lists. DMARC is about organizational identity. In fact, I was contacted about my DMARC primer and told that I didn’t mention that it’s not about domains, it’s about organizations.
The way I read the DMARC spec, it is all about organizational identity. The underlying theme being that the domain name is linked to a particular organization and everyone using email at that domain has some official relationship with that organization. I’ve always read the spec mentally replacing organization with corporate brand. This was for brands and organizations that strictly control how their domains are used, who can use those domains and how the mail is sent with those domains.
I never expected any mailbox provider or commercial ISP to publish a p=reject message as it would just break way too much of the way customers use email. And it did break a lot of legitimate and end user uses of email. Many organizations have had to scramble to update mailing list software to avoid bouncing users off the lists. Some of these upgrades have broken mailbox filters, forcing endusers to change how they manage their mailboxes.
Even organizations see challenges with a p=reject message and can have legitimate mail blocked. At M3AAWG 30 in San Francisco I was talking with some folks who have been actively deploying DMARC for organizations. From my point of view anyone who wants to publish a DMARC p=reject should spend at least 6 months monitoring DMARC failures to identify legitimate sources of email. The person I was talking to said he recommends a minimum of 12 months.
This is just an example of how difficult it is to capture all the legitimate sources of emails from a domain and effectively authenticate that mail. For a mailbox provider, I think it’s nearly impossible to capture all the legitimate uses of email and authenticate them.
It remains to be seen if the other mailbox providers imitate Yahoo! and AOL or if they push back against the use of DMARC reject policies at mailbox providers. Whatever the outcome, this is a significant shift in how email is used. And we’re all going to have to deal with the fallout of that.

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Is gmail next?

I’m hearing hints that there are some malware or phishing links being sent out to gmail address books, “from” those gmail addresses. If that is what’s happening then it’s much the same thing as has been happening at Yahoo for a while, and AOL more recently, and that triggered their deployment of DMARC p=reject records.
It’s going to be interesting to see what happens over the next few days.
I’ve not seen any analysis of how the compromises happened at Yahoo and AOL – do they share a server-side (XSS?) security flaw, or is this a client-side compromise that affects many end users, and is just being targeted at freemail providers one at a time?
Does anyone have any technical details that go any deeper than #AOLHacked and #gmailhacked?

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April: The month in email

April was a big month of changes in the email world, and here at Word to the Wise as we launched our new site, blog and logo.
DMARC
The big story this month has been DMARC, which started with a policy change Yahoo made on April 4 updating their DMARC policy from “report” to “reject”. We began our coverage with a brief DMARC primer to explain the basics around these policy statements and why senders are moving in this direction. We shared some example bounces due to Yahoo’s p=reject, and talked about how to fix discussion lists to work with the new Yahoo policy. We gathered some pointers to other articles worth reading on the Yahoo DMARC situation, and suggested some options for dealing with DMARC for mail intermediaries. Yahoo issued a statement about this on April 11th, explaining that it had been highly effective in reducing spoofed email. We also noted a great writeup on the situation from Christine at ReturnPath. On April 22nd, AOL also announced a DMARC p=reject record.  We talked a bit about who might be next (Gmail?) and discussed how Comcast chose to implement DMARC policies, using p=reject not for user email, but only for the domains they use to communicate directly with customers. We expect to see more discussion and policy changes over the next few weeks, so stay tuned.
Spamtraps
We wrote three posts in our continuing discussion about spamtraps. The first was in response to a webinar from the DMA and EEC, where we talked about how different kinds of traps are used in different ways, and, again, how spamtraps are just a symptom of a larger problem. Following that, we wrote more about some ongoing debate on traps as we continued to point out that each trap represents a lost opportunity for marketers to connect with customers, which is really where we hope email program managers will focus. And finally, we tried to put some myths about typo traps to rest. As I mentioned in that last post, I feel like I’m repeating myself over and over again, but I want to make sure that people get good information about how these tools are used and misused.
Security
We started the month by saying “Security has to become a bigger priority for companies” and indeed, the internet continued to see security breaches in April, including the very serious Heartbleed vulnerability in SSL. In the email world, AOL experienced a compromise, which contributed to some of the DMARC policy changes we discussed above. In a followup post, we talked about how these breaches appear to be escalating. Again, we expect to hear more about this in the next weeks and months.
Best Practices
Ending on a positive note, we had a few posts about best practices and some email basics. We started with a pointer to Al Iverson’s post on masking whois info and why not to do it. Steve wrote up a comprehensive post with everything you ever wanted to know about the From header and RFC5322. I talked about how companies ignore opt-outs, and why they shouldn’t. I shared a really good example of a third-party email message, and also talked about message volume. And finally, we talked about how and why we warm up IP addresses.
Let us know if there’s anything you’d like to hear more about in May!

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