Hopefully by now you have read our article about what the big Yahoo DMARC p=reject rejection means for you and your email. And you may or may not be aware that yesterday AOL did the exact same thing, also publishing a DMARC policy of p=reject, which means, essentially, “reject any email coming from a yahoo.com or aol.com address if it was not sent through a Yahoo or AOL mail server.”
What you may not yet realize is that this has broken various mailing lists in unanticipated ways. Basically, if a receiving mail server is DMARC compliant, that means that the server will reject (bounce) any email from a Yahoo or AOL address that isn’t actually sent from a Yahoo or AOL server.
Now, if that rejected email happens to be mailing list email – i.e. mail that was sent through a mailing list, then the mailing list software will receive the bounce.
And, and this is very important, most mailing list software is set to automatically remove any email address that bounces email.
So is a lot of other mailing software, including autoresponder software, so this has the potential to affect a lot of business email.
Today we heard from someone with Google that Google has pushed an update to the Google Groups mailing software to address this issue.
What their fix does is rewrite the “from” address if the original “from” address is from yahoo.com or aol.com (and presumably from any future email provider who publishes a p=reject policy for DMARC). They then move the original “from” address to an “X-Original-From’ x-header.
As we understand it, this will have the effect of having the working “from” address be a Google Groups (or at least a Google) address, with reference to the original sender, while the actual original “from” address will be kept intact within the X-Original-From header.
To read more about this issue, read the following articles (some here, some at our Internet Patrol publication):