> -----Original Message-----
> From: Viktor Dukhovni via Postfix-users <[email protected]>
> Sent: Monday, March 23, 2026 9:26 AM
> To: [email protected]
> Subject: [pfx] Re: Sender Domain Configuration Help
> 
> On Mon, Mar 23, 2026 at 06:16:46AM -0400, Scott Hollenbeck wrote:
> 
> > [SAH] Thanks, I did read that before sending my original message. I
> > provided the problem statement above. I'm trying to configure postfix
> > so that the domain part of the sender email address is "dnsmon.net".
> > What's being used is "juno", the host name.
> 
> Well, Postfix only gets to set the domin part of the sender address
> when it is not already set by the MUA or command-line program
> that submitted the message.
> 
> > 2026-03-22T18:29:00.796297-04:00 localhost postfix/pickup[32729]:
> C241860603C3: uid=1000 from=<sah62@juno>
> 
> Almost certainly, the "@juno" was the sender address passed via
> "sendmail -f", and was not added by Postfix, which would append
> $myorigin.

[SAH] Ok. Where that value came from may be a topic for an Ubuntu forum.

> > 2026-03-22T18:29:00.811585-04:00 localhost postfix/qmgr[32730]:
> C241860603C3: from=<sah62@juno>, size=366, nrcpt=1 (queue active)
> 
> It seems you have the default "append_dot_mydomain = no", so "@juno"
> survives unmodified.  My advice is set the system hostname to a
> fully-qualified name and rewrite it if necessary, because some
> software may default to appending the system hostname to unqualified
> addresses.
> 
> > append_dot_mydomain = no
> 
> My choice may be outside the mainstream, but I generally set this to "yes".

[SAH] I tried that. It changed "juno" to "juno.net". Closer, but still not 
correct.

> > myorigin = /etc/mailname
> 
> That's a Debianism, but assuming that name is not "juno", we have clear
> evidence that that problem sender address is already in place before
> Postfix gets to handle the message.

[SAH] Understood. I described the contents of that file it my original message. 
It contains "dnsmon.net".

I tried changing the value of the hostname (in /etc/hostname) from "juno" to 
"dnsmon.net". That fixed the sending domain issue, but I still need to figure 
out why my server configuration is incorrect. At least I know the problem isn't 
with postfix. Thanks, Viktor.

Scott

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