[Discuss] DMARC issue, Yahoo and beyond

[blu at nedharvey.com (Edward Ned Harvey (blu))]

> From: discuss-bounces+blu=nedharvey.com at blu.org [mailto:discuss-
> bounces+blu=nedharvey.com at blu.org] On Behalf Of Bill Horne
> 
> I just posted from a Yahoo account, but I don't think that's the issue:
> the problem, if I understand it, is that other subscribers to this list
> who have gmail, hotmail, etc., accounts where /their/ ISP enforces DMARC
> /will/ /not/ /see/ my post, because *their* email server will reject my
> email, since the Mailman robot modifies the "Subject" line and does
> other things that break DMARC. Someone correct me if I've got that wrong ...

That's only half the story.  The less important half.  Here's the rest:

A recipient on gmail (or whatever) will reject the post from the yahoo user, and *send a bounce.*

Now, if you're a mailing list, with a bunch of members, and one (or several) of your subscribers bounces, what do you do?  You very likely remove that user from the list.  I am pretty sure the mailman default behavior is to unsubscribe users that bounce, after a few tries.