[mu4e bug] User-Agent header not set

[manphiz]

Describe the bug

It looks like mu4e doesn't set User-Agent header anymore. It used to do that when I was using 1.8.x. I stopped using it for a while and started trying it again since 1.12.5 and I can no longer see User-Agent being set. I suspect this may be happening for earlier versions as well.

How to Reproduce

Sending a mail and show all headers, and there is no User-Agent set.

Environment

Debian Linux stable (Bookworm) Emacs 29.4 mu4e 1.12.6

Checklist

• [x] you are running either an 1.10.x/1.12.x release or master (otherwise please upgrade)
• [x] you can reproduce the problem without 3rd party extensions (including Doom/Evil, various extensions etc.)
• [x] you have read all of the above

Possible Cause

'User-Agent is included in the draft header when message-newsreader is set[1]. However, the only place that it's being set is at [2] where it's let-bounded, so it has no effect on the code at [1].

[1] https://github.com/djcb/mu/blob/f101e0d4ca86b46718e0e3d46dee04a6f8b77bc4/mu4e/mu4e-draft.el#L573 [2] https://github.com/djcb/mu/blob/f101e0d4ca86b46718e0e3d46dee04a6f8b77bc4/mu4e/mu4e-draft.el#L517

[manphiz]

I have a tentative fix at https://github.com/djcb/mu/pull/2751, though I'm not sure whether this is the best way to do this. Please advice. Thanks!