On Mon, Sep 09, 2024 at 01:53:27AM +0200, Christian Schulte wrote:
> >   Content-Type: text/plain; charset=UTF-8
> >   Content-Transfer-Encoding: 7bit
>
> That is correct and not related to Thunderbird. As long as there are
> [...]

You're right.  Reading about it I find out this combination could be
necessary in case you use 7-bit representations of utf-8 characters
(other than quoted-printable or base64,) eg html code characters.

> 
> Sorry for the noise. This isn't a MUA support forum.

Next time you want to check which headers are generated by your MUA (and
which ones by your MTA) you don't need to send a message to this lists
and ask others, just send a message to yourself, then in the copy your
MUA saves to your disk you can verify which headers were generated by
your MUA, in the copy you receive from you MTA you can verify which
headers were later added by your MTA.

Anyway, my slightly related question was: how did you managed to include
a In-Reply-To header using a plain smtpd(8) command ('sendmail -t').


> 
> -- 
> Christian
> 
> 

-- 
Walter