Johannes Schindelin <Johannes.Schindelin@xxxxxx> writes: > Date: Fri, 04 Oct 2019 08:09:25 -0700 (PDT) > [...] > X-Google-Original-Date: Fri, 04 Oct 2019 15:09:10 GMT > [...] > > I am fairly certain that the latter is the actual `Date:` line sent to > GMail, and GMail just decides that it will not respect it. If the submitting program said "Fri, 04 Oct 2019 15:09:10 +0000 (GMT)" instead of "Fri, 04 Oct 2019 15:09:10 GMT", that would match the format the MTA produced itself, I guess. I am kind-of surprised if the problem is the use of the obs-zone format (RFC 2822 page 31), but anything is possible with GMail X-<. How does send-email write that date header? Matching that would be probably the most appropriate, if possible, given that GGG was written for send-email refugees, I guess ;-) Here is what its format_2822_time sub does, so +0000 without any textual zone name, it is. return sprintf("%s, %2d %s %d %02d:%02d:%02d %s%02d%02d", qw(Sun Mon Tue Wed Thu Fri Sat)[$localtm[6]], $localtm[3], qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec)[$localtm[4]], $localtm[5]+1900, $localtm[2], $localtm[1], $localtm[0], ($offset >= 0) ? '+' : '-', abs($offhour), $offmin, );