[sclug] Auto-reply for old address with maildrop

[Roland Turner SCLUG]

On Sun, 2006-03-19 at 09:11 +0000, Patrick wrote:

> What does reply 550 mean?

>From RFC 2821 4.2.2:

  550 Requested action not taken: mailbox unavailable
     (e.g., mailbox not found, no access, or command rejected
     for policy reasons)

In fact, looking a little further forward:

  551 User not local; please try <forward-path>
     (See section 3.4)

It's still a hard failure code, but one specifically designed for the
reporting of change-of-address. Elsewhere it is pointed out that, of
course, you cannot in fact rely upon this information being reliably
communicated to the sender.

Certainly, this is a lesser of two evils situation:

- Originating a new "my address has changed" message breaks all kinds of
stuff (naturally one would unsubscribe all mailing list subscriptions
that one knew about first, but consider also, say, bug reports ever
filed with any instance of BTS or Bugzilla run by any project) and
provides a lever for an attacker or spammer.

- Using a 551 carries some small risk that correspondents will (a) not
actually get the change-of-address notification or possibly even (b) not
know that their message didn't get through.


- Raz