[Mailman-Users] DMARC and From header munging

[Stephen J. Turnbull]

Lindsay Haisley writes:

 > Mailman to change the From: address to a VERP-like address with the
 > author's address encapsulated within an address @ the list server.
 > Any mail received by the list server for this address would have
 > its address parsed by Mailman and be redirected to the original
 > author's real email address.  Would this pass RFC compliance?

Technically, it probably does.  The problem is that Mailman doesn't
handle those mails, the MTA does.  It would be reasonably easy to set
up a filter and have the MTA pass the message to that filter.

It's very ugly, though, especially if for some reason you have no
display name to work with.

A bigger problem, as stated what you've done is to set up an open
relay.  So you would need to either maintain a database of valid
addresses forever, or do some crypto trickery so that only valid
addresses would be forwarded.  The latter would involve key
management, etc.

N.B. I read a very similar suggestion somewhere, probably in the DMARC
Internet-Draft or in their FAQ.