Seeing more bounces for addresses? It’s not just you.

Over the last couple of days, mail from addresses has been “bouncing” a lot more than usual, often with error messages about “policy” or “DMARC” problems. This is especially true for messages involving mailing lists or forwarding from other addresses.

If you see this happening, it isn’t because of anything wrong on your end, or our end. It’s happening all over the Internet.

Why is this happening?

Yahoo recently made an unprecedented change to their mail system. They’ve added a new policy that says that all mail from “” addresses must be sent through their servers. In fact, it’s stricter than that: it effectively says that all mail claiming to come from addresses must pass only through their servers, without passing through any other servers.

This new policy means that mail should be rejected if any message using a “From:” address is:

  • Resent through a mailing list; or
  • Resent using a mail forwarding system that modifies the message; or
  • Sent via any non-Yahoo server, such as a contact form on a Web site

… and then gets delivered to an ISP that honors this policy, including Gmail, AOL, Comcast, and Yahoo themselves.

Needless to say, all three situations are very common, and many people are complaining that Yahoo has effectively broken e-mail for all their users (an Internet search for “Yahoo DMARC” shows much more).

What can I do?

If you run a mailing list, there’s nothing you can do about the extra bounces you’ll get when members with a “” address send to your list for now. The authors of mailing list software, including the Mailman software that’s available on our servers, are working to make changes to avoid the problem in future versions. (We’ll install an updated version of Mailman as soon as possible after it’s released.)

If you’re seeing it happen because you’ve installed contact form software on your site that lets users send mail from their “” address to another ISP, you can avoid the problem by delivering the contact form mail to a mailbox on our servers instead of the other ISP. Alternately, technically advanced users can modify how their form works so that instead of sending a message “From:”, it sends it “From:, Reply-To:”, where “” is your own domain name. (We’ve updated the preinstalled FormMail script on our servers to work this way.)


  1. Apparently, Yahoo isn’t going to fix this:

    In fact, Yahoo’s change is likely to be implemented by Outlook/Hotmail, Gmail, et. al.

    My organization relies very heavily on email discussion lists (not hosted at Tiger Tech), and about a quarter of our list participants use email addresses. So we are very heavily impacted.

    I gather that there is already (or soon will be) a patch for Mailman. I know that Sympa is also looking at a possible patch. In the meantime, as a temporary fix some installations of Mailman and Sympa have been modified to reject all posts from with a custom message referring to the DMARC problem.

    On the other hand, we’re not affected at all by the problem this poses for contact forms. Those are already auto-forwarded through Tiger Tech’s mail servers.

  2. I’ve also been dealing proprietary line break formatting from Yahoo for months. When i send in HTML, I have 2 send 2 mailings: 1 with standard formatting to everyone not using Yahoo, & 1 with double paragraph breaks for Yahoo users only.

    If I don’t Yahoo users get 1 long paragraph…………

    Gmail has also gone to a different type of proprietary line break formatting; unlike most providers they no longer automatically balance line breaks.