I will consider "fixing" this for Mailman 2.1.26, but I note that the retry loop is not "infinite". It is one retry every DELIVERY_RETRY_WAIT (default one hour) for DELIVERY_RETRY_PERIOD (default 5 days) before giving up and returning failure. Granted, this is perhaps 719 unnecessary retries, but is far from "infinite".
Also note the problem of an oversize digest can be entirely avoided by setting digest_size_threshhold to a reasonable maximum.
Finally. consider what happens if this is considered a "hard bounce". It means every innocent digest member whose ISP rejects the oversize digest with a 552 will record a bounce for that digest. In extreme cases, it could result in users delivery being disabled and ultimately unsubscribed through no fault of their own.
A similar problem could exist with overly large individual messages, and this can also be easily avoided by setting max_message_size to a reasonable value and not approving excessively large posts.
** Changed in: mailman Importance: Undecided => Low
** Changed in: mailman Status: New => Triaged
** Changed in: mailman Assignee: (unassigned) => Mark Sapiro (msapiro)