DMARC and Mailing Lists
In early April 2014, Yahoo changed their email policies (and called this change an aggressive level of DMARC) in an effort to stop spam and phishing against it's users. This policy change requires Yahoo users to change the way they use their email services and has caused widespread problems with users throughout the Internet, including May First/People Link Members.
Essentially, via this policy change, Yahoo is telling the world: Don't accept any email message from an address that ends in yahoo.com unless it was directly sent by our servers.
Unfortunately, that includes email messages sent by our email servers.
May First/People Link has mitigated this problem by changing the way our email list servers works.
If an email message is received from an email address that uses this aggressive DMARC setting, then the from address will be changed so it appears to be coming from the email list, rather than from the original sender.
In addition, if any email messages still manage to slip through (perhaps they were sent via a CiviCRM install or any other program using bulk.mayfirst.org), May First/People Link is modifying messages sent to our email list servers from Yahoo email addresses - we are re-writing the From address to be from a mayfirst.org email account rather than the original yahoo address. As a result, you may see messages posted to your email list with a From address like:
"Jose Garcia <jose.garcia@yahoo.com> (relay)" <strict-dmarc@mayfirst.org>
If you reply to this email message, the reply will go to: strict-dmarc@mayfirst.org and the message will bounce.
Technical Details
Yahoo has published information to all mail providers telling them to reject any message that claims to be from Yahoo that does not properly prove it was sent from a Yahoo server. When you send a message to an email list, the email list will resend that message to all subscribers to that list. As a result, the message is not being sent from a Yahoo server, it is being sent from the server running the mailing list. When evaluating reception of email, destination servers are not able to verify that the message was originated from Yahoo, so they reject the message.
For more information, please see:
http://www.spamresource.com/2014/04/up-in-arms-about-yahoos-dmarc-policy.html
