On 12/5/23 10:08, Thomas Ward via Mailman-users wrote:
We use a multi-hop SMTP system to go from the inside of our network out to the Internet at the domain test.lists.example.com.
The setup is this way for ingress:
{EXTERNAL} -> MS365 (relay/antispam) -> MS On-Prem (via 365 Connector) -> Mailman for delivery to listserv
Egress is this:
Mailman -> Postfix SMTP Relay (smtpproxy) -> INTERNET
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When a message is sent an invalid list (we'll call it invalid@test.lists.example.com) we end up with a nasty side effect in the system. The "no such recipient" response gets sent to the smtpproxy machine and then *it gets redelivered back to Mailman* as a redelivery as if it isn't accepting a permanent-failure condition code.
I don't understand why this is happening. Whatever MTA is seeing the "no such recipient" status and creating the response DSN should be sending it to the envelope sender of the original message so it should not be sent to the invalid mailman address. Is one of the MTAs in the delivery chain to Mailman rewriting the envelope sender?
What are the MTA log messages from all the MTAs whos logs you have access to?
-- Mark Sapiro <mark@msapiro.net> The highway is for gamblers, San Francisco Bay Area, California better use your sense - B. Dylan