dap1--- via Mailman-users writes:
I am getting mail bounced from yahoo and gmail smtp servers with this message:
554: Message not accepted due to failed RFC compliance. Too many From headers. See https://senders.yahooinc.com/smtp-error-codes#rfc-compliance-failures
Waste of time, no reference to what RFC may have been violated. And multiple addresses in From is conformant, although unusual. From RFC 5322 (the only RFCs mentioned by Yahoo!'s sender requirements are 5321 and 5322);
from = "From:" mailbox-list CRLFwhich means what you would think it means, more than one is OK. I'm guessing they mean RFC 7489 defining the DMARC protocol which does specify that a message can't satisfy "From alignment" with more than one From address. But that's conformant if all From addresses are p=none domains.
What would cause mailman to build too many from headers when distributing email? It appears the from address is repeated 5 times in the from field. I'm guessing it is something in my configuration but what and where?
I agree with Mark, it's not Mailman. I checked the code and I can only find two cases where Mailman alters the From header, anonymous list and Munge From. Both involve *replacing the entire content* of the header with the List-Post address (and a comment indicating the original address for Munge From).
Please check the incoming messages. I think that what *may* have happened is that
- the message as received by your site already had several From addresses,
- Mailman condensed that to one for the purpose of the DMARC check,[1]
- that one was a DMARC "p=none" address,
- Mailman left From as received when it distributed the post, and
- Yahoo! et al rejected it.
Footnotes: [1] I'll be looking at this in more detail, but as I read it now we only check the first address of multiple addresses in From. I think that either we should reject such messages unless DMARC Mitigation is None, or we should check all the addresses for p=none and reject if any have a different policy.
-- GNU Mailman consultant (installation, migration, customization) Sirius Open Source https://www.siriusopensource.com/ Software systems consulting in Europe, North America, and Japan