bug#53467: 29.0.50; Wishlist: smtpmail should be asynchronous

[Lars Ingebrigtsen <larsi@gnus.org>]

It should be pretty easy to implement using process filters, but perhaps
it could also be done by using threads?

The main problem is doing error handling, I think.  When replying to a
message in Gnus, for instance, after hitting `C-c C-c' in the Message
buffer, we then mark the message as replied-to in the Gnus summary
buffer, put it into the archive folder, etc.  But if then smtpmail is
unable to send the message, because the To header is invalid, for
instance, what should then happen?  Ideally you'd then land back in the
Message buffer and continue editing, and then resend the message.  But
the Message buffer may not exist at that point.

And even more ideally, the message shouldn't be marked as replied-to
until smtpmail has finished delivering the message, but that's even more
tricky -- Gnus may not even be running at that point.

So making smtpmail asynchronous is easy, but making a useful framework
around that is harder.


In GNU Emacs 29.0.50 (build 4, x86_64-pc-linux-gnu, GTK+ Version 3.24.31, cairo version 1.16.0)
 of 2022-01-22 built on giant
Repository revision: 41846901e22e824f02796012164c51df0297c6ec
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12014000
System Description: Debian GNU/Linux bookworm/sid


-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no