The nice folks over at Postmark shared a new deliverability resource last week. The SMTP Field Manual. This is a collection of SMTP responses they’ve seen in the wild. This is a useful resource. They’re also collecting responses from other senders, meaning we can crowdsource a useful resource for email deliverability folks.
There are a bunch of them and they’re all worth reading.
I have more to say about DMARC, both in terms of advice for senders and list managers affected by this, and in terms of the broader implications of this policy decision. But those articles are going to take me a little longer to write.
How widespread is the problem? Andrew Barrett publishes numbers, pulled from his employer, related to the number of senders using @yahoo.com addresses in their commercial emails. Short version: a low percentage but a lot of users and emails in raw numbers.
What can mailing list managers do? Right now the two answers seem to be stop Yahoo.com addresses from posting or fix your mailing list software. Al has posted how he patched his software to cope, and linked to a post by OnlineGroups.net about how they patched their software.
A number of people are recommending adding an Original Authentication Results header as recommended in the DMARC.org FAQ. I’m looking for more information about how that would work.
For commercial mailers, there doesn’t seem to be that much to do except to not use @yahoo.com address as your header-From address. Yes, this may affect delivery while you’re switching to the new From address, but right now your mail isn’t going to any mailbox provider that implements DMARC checking.
One other thing that commercial mailers and ESPs should be aware of. Depending on your bounce handling processes, this may cause other addresses to bounce off the list. Once the issue of the header-From address is settled, you can reactivate addresses that bounced off the list due to authentication failures since April 4.
In the comments of last week’s Wednesday question John B. asked
Read MoreLast night (Mar 29, 2017) between about 8pm Eastern and 9:30pm Eastern AOL suffered a technical issue. Every email sent to them received a “Recipient address rejected” reply. One example of the error message:
Mar 29 20:45:12 p2-lvmail11 lsb1-99-208-250/smtp[22251]: A88DFC2DBE9: to=<redacted@aol.com>, relay=mailin-01.mx.aol.com[64. 12.91.195]:25, delay=0.18, delays=0.01/0/0.14/0.03, dsn=5.1.1, status=bounced (host mailin-01.mx.aol.com[64.12.91. 195] said: 550 5.1.1 <redacted@aol.com>: Recipient address rejected: aol.com (in reply to RCPT TO command))
The issue was brought to AOLs attention and things were fixed rapidly after that. An AOL representative has stated that these were invalid replies and that addresses do not need to be removed from future emails.
Most of the ESPs are aware of this and are working to restore any bounced addresses to their users. At some places this requires manual intervention, so it’s taking some time to get all the addresses restored.
This is one of the reasons that our best bounce handling recommendations are not to remove an address for a single bounce – sometimes the ISPs have technical problems. Like the time a routing failure meant a major ISPs MX machines couldn’t reach their authentication servers to get the list of active users. Or the time all an ISPs MXs were removed from DNS. A lot of the internet is still managed manually, and despite extensive safeguards put in place bad things can, and do, still happen. Usually these problems are resolved quickly and mail starts flowing again.
Morning advice: Do not deactivate addresses that bounced at AOL last night.