See the below email chain - I thought it would be a good idea to send
this to the ietf-smtp mailing list as well.
---------- Forwarded message ---------
From: John Levine <johnl(_at_)taugh(_dot_)com>
Date: Thu, Jul 9, 2020 at 9:59 PM
Subject: Re: [dispatch] Forced SMTP redirects
I'd suggest reposting this to the ietf-smtp list where people who've
been around a lot longer than I have can explain why nobody implements
551 redirects (and as far as I can tell, nobody ever did) and there is
assigning a different response code won't change that. It may seem
like a good idea, but turns out not to work in practice.
FWIW I looked through the last seven months of my mail server's logs
and the total number of 551 responses is zero.
PS: There have been some attempts at setting up change-of-address
services where you can register old and new addresses, so mail servers
could query them after getting a 550, and they never went anywhere either.
See US Patents 6,654,789, 6,892,222, and 7,080,122.
On the other hand, a lot of mail systems now let users keep their
addresses after they leave, ranging from ISPs like Comcast and
Spectrum to universities who turn student addresses into alumni
addresses. They let you forward the mail, or you can add it to
the list of accounts your MUA checks, or either or both.
I have published a new internet-draft that might be of interest.
As always, its on the Datatracker:
ietf-smtp mailing list