Comment 2 for bug 558128

I experienced a problem with Mailman 2.1.24 as a result of this.

A list received several large messages in one day that made the size of a digest exceed 90 MB. When Mailman sent the digest, it got back this SMTP error:

 552 5.3.4 Message size exceeds fixed limit

And logged this to logs/smtp-failure:

 SMTP session failure: 552, 5.3.4 Message size exceeds fixed limit, msgid: <...

Unfortunately, the SMTPDirect.py code mentioned in this bug report special-cases "552" errors to treat them like "452" errors, resulting in Mailman trying to redeliver this message in an infinite loop until I removed it from the queue.

The special-casing is apparently to work around a documentation error in RFC 821 that was corrected in RFC 2821: The fear was that MTA authors had followed the documentation error and were returning a 552 instead of a 452 for the case of "too many recipients in this session".

I would expect that few-to-no mail servers in active use have such a problem anymore; the original bug here requesting the removal of the workaround code is 13 years old. At this point, it's very likely that the workaround code merely makes Mailman wrongly retry legitimate 552 "Message size exceeds fixed limit" deliveries over and over.

The obsolete code should probably be removed. A trivial patch against Mailman 2.1.25 is attached.