First of all, what I'm trying to point out is a detail of how smptd(8)
handles headings.  As I see it, it's of general interest and I am not
getting off topic or talking nonsense, if you or someone else thinks so
just ignore my message.  Surely someone will know how to take advantage
of what I am saying.

On Tue, Sep 10, 2024 at 12:47:19PM +0200, Christian Schulte wrote:
> On 10.09.24 12:07, Walter Alejandro Iglesias wrote:
> > On Tue, Sep 10, 2024 at 01:10:39AM +0200, Christian Schulte wrote:
> >> On 09.09.24 11:54, Walter Alejandro Iglesias wrote:
> >>>
> >>> 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').
> >>>
> >>
> >> By copying the message id from the archive into vi(1) and writing it by
> >> hand. sendmail(8) adds missing message-id and date headers.
> > 
> > You helped me to find something curious.
> > 
> > First of all, the message you sent with the sendmail command, besides
> > In-Reply-To and References (which are not added by opensmtpd) shows a
> > Message-ID which is also not generated by opensmtpd:
> > 
> >   Message-ID: <29b681b5a4b153c2@x500.schulte.it>
> 
> There is no References header, because I did not type it into vi(1). Of

Your message in question includes also this header:

  References: <cec236be0424d05f48a9e9fda180bf5d@poolp.org> 

> course the message id header has been generated by OpenSMTPD.
> 
> x500$ cat /etc/myname
> 
> x500.schulte.it

You're right in this, the 'x500' confused me, sorry.

> 
> > This tells me that you pasted more than one header in the file.
> 
> No. I did not.

I count below *four* headers and the first three are among the ones
recongized by smtpd as such.

> 
> From:
> To:
> Subject:
> In-Reply-To:
> 
> Nothing more than this. Message-ID and Date got added by OpenSMTPD,

OpenSMTPD *always* adds Message-ID and Date (if your MUA didn't).  What
I'm trying to notice is that In-Reply-To got added correctly thanks to
you also added From, To and Subject.  Try sending a message to yourself
adding only In-Reply-To and see what happens.


-- 
Walter