On 12/14/23 14:19, bob B via Mailman-users wrote:
I am running MM3 and have a list that has users from different organizations and email domains.
So let's say I am orga.com and hosting mailman Bill is borg.com Cindy is mew.com
When Bill sends a message to my MM3 list it gets sent out, However, cindy's email system rejects it cause it sees the message is sent from Bill@borg.com but it came from my MM3 server which is under orga.com, so it rejects it.
You need to apply DMARC mitigations. Normally mitigations are only applied if the From: domain publishes DMARC p=reject or p=quarantine, but recently this has become problematic. For example, gmail.com pubpishes DMARC p=none yet google servers effectively apply p=reject to mail From: gmail.com.
Mailman >= 3.3.9 and Postorius >= 1.3.9 allow setting dmarc_addresses to a list of email addresses and regexps matching addresses and domains to which DMARC mitigatations will be applied regardless of puublished policy. For older releases and for cases where domains are not known in advance one can always set dmarc_mitigate_unconditionally True to apply mitigations to all mail.
-- Mark Sapiro <mark@msapiro.net> The highway is for gamblers, San Francisco Bay Area, California better use your sense - B. Dylan