On 2021-02-16, Jeff King wrote:
> … It matches alias config, credential config, and perhaps others
> as "treat this as a shell command".

I will have to take closer look at the '!' prefix in other git parts,
but I like that approach.

> (I'd prefer to just have $smtp_program or similar as that signal
> instead, but it doesn't seem worth trying to retrofit it now).

That would also be my preference, but it would be a larger change
and I'm not currently confident enough to go this route.

From the points and ideas raised (and btw, thanks a lot for those),
the easiest one seems to be treating $smtp_server as path options,
the cleanest one a new $smtp_program options,
and the middle ground being adding support for '!' prefix.
Unless someone beats me to it, I will try to throw together a patch,
aiming for now for the '!' prefix and falling back to path option
– as this is potentially my first contribution here,
I'll see how it goes.
--
Jan Staněk – Khardix