smtpmail.el feature request: envelope-sender from From:

[Justus-bulk@Piater.name]

Hi -

I'd like the envelope-sender to be taken from the From: field.

This is handy if you have several e-mail addresses, some of which are
aliases and have no associated mail server, and you want to send to
members-only mailing lists that check list membership by
envelope-sender/Return-Path.

This is possible by letting (smtpmail-mail-address (mail-fetch-field
"from")) in smtpmail-send-it, which I use for now with a hacked
version of smtpmail.el.

Of course, this should be configurable, as message.el allows it with
sendmail, see message-sendmail-envelope-from. The same mechanism
should be fairly easily implemented for smtpmail, by replacing my
quick hack by a few more lines of code, perhaps by using
mail-envelope-from in the same way as message-sendmail-envelope-from
(with a 'header value), or by using message-sendmail-envelope-from.

Would this be reasonable?

Besides, why are there two separate variables (mail-envelope-from and
message-sendmail-envelope-from) for seemingly identical purposes?

Cheers,
Justus