[Mailman-Users] Who authored the message?

[John Levine]

>So, addresses get rewritten as:
>
>From: yahoousername-AT-yahoo.com at mydomain.com

>My sense is that someone could come up with arguments as to why this is
>a bad idea, ...

It's a bad idea for the same reason that all of the other anti-DMARC
hacks are a bad idea, they break the existing usage of mail.

Under the current unpleasant circumstances, it's not much worse than
any other, give or take what you do with the replies.  Do you forward
them back to the original user?  Reject with a mysterious failure
code?  Discard them?

RFC nitpick: the mailbox part of an address is limited to 64
characters, so this has some risk of violating that limit, and there
are a few MTAs that care.  The domain part can be up to 256 which is
why I put my noise there.

R's,
John