Public bug reported:
The LMTP server currently does a sanity check on the To field of the incoming message, to ensure that it is addressed to a valid mailing list. This check ignores acceptable aliases, but it should honor them.
** Affects: mailman Importance: Undecided Status: New
** Tags: mailman3
Does "the To field of the incoming message" mean the RCPT TO argument of the LMTP session? Or the "To:" header of the message. I think it should mean the former, since the latter needn't be related at all, if the list permits BCC.
BCC is the whole point of this bug. If a list requires 'explicit destination', the list address or an acceptable alias must be in the To: or Cc: headers of the message. The bug says acceptable aliases aren't checked and it means against the To: or Cc: headers.
Checking against the envelope recipient is irrelevant since if the list weren't the envelope recipient of the message, the list's chain wouldn't be seeing the message in the first place.
This bug has been moved to the new gitlab repo here: https://gitlab.com/mailman/mailman/issues/69