Sam Varshavchik <mrs...@courier-mta.com> writes:

So qmail is out of the play.

Oh, it can do that, but it fails to communicate its trouble back, because it exits with EX_TEMPFAIL even for PERMANENT error conditions, like: no such user (EX_NOUSER).

The MTA relies on its MDA to communicate trouble back, waiting for the queue entry to expire just does not cut it.

Some MTAs allow you to "bless" maildrop to the general delivery backend, and don't bother to check. This is usually the more efficient approach compared to tricking the regular delivery backend into using maildrop.

The interface is there, it's sysexits.h, and maildrop defeats it for no good reason. Some MTAs (Postfix) don't bother to reject mail for non-existent users at the /usr/sbin/sendmail interface, and in this case, mail will ly around for a week or so, when it should instead bounce right away, which it would if maildrop bothered to exit(EX_NOUSER).

TECHNICAL reasons to refuse my patch like "it can return EX_NOUSER even for temporary failures" are fine, I will look into things and fix them. POLICY reasons just impair the usefulness of maildrop. And that's sad.