bug#25436: 25.1; sendmail does not add a Date: header in FCC

[Glenn Morris]

Eli Zaretskii wrote:

> The important question is why Date is not generated in
> the mail buffer in your case.

Are you sure?
emacs -Q
C-x m
  -> No Date: header in mail buffer.

This seems correct, because if Date was added then, it might have no
relation to when the message was sent.

smtpmail-send-it adds Date: at sending time.

sendmail.el has always relied on "sendmail" adding Date:, AFAICS.
mail-do-fcc only adds Date: for Babyl files.
Perhaps the date in the mbox From line was assumed to be good enough for
the alternative case.