bug#22754: 25.1.50; Rmail does not follow RFC 2822

[Glenn Morris]

Eli Zaretskii wrote:

>> From: Marcin Borkowski <mbork@mbork.pl>
>> Date: Sun, 21 Feb 2016 11:28:27 +0100
>> 
>> Rmail inserts lower-case field names in the header, which goes against
>> RFC 2822 (pp. 22 and 23, see
>> https://tools.ietf.org/html/rfc2822#page-22).  It seems that the problem
>> affects Cc: and In-reply-to: fields.
>
> I use Rmail all the time, and these headers are capitalized in my
> reply messages.  So please provide a recipe starting from "emacs -Q",
> there could be some other factor at work here.

I assume it was a theoretical analysis...

With sendmail-user-agent, mail-setup inserts "Cc" and "In-reply-to"
directly (apparently the latter should be "In-Reply-To"?), ignoring the
case passed via other-headers.

With message-user-agent, message-mail explicitly uses capitalize on all
headers.

I suppose there's no guarantee that some other mail-user-agent won't use
the headers as supplied, but perhaps that would be a bug in the
user-agent?