On Thu, Jan 08, 2026 at 11:51:39AM -0500, Dennis Putnam via Postfix-users wrote:
> > That said, why do you feel you need to debug the smtpd process? That's
> > rarely needed unless you're experimenting with private patches that
> > aren't working...
> >
> Thanks. It was simply the new line after the $ that was the problem. I am
> now getting the output but it was not what I expected. I am having trouble
> with my ISP rejecting email generated by mailman3. I wanted to collect the
> session exchange between my postfix and my ISP relay. This is apparently not
> doing what was hoping. Is there some other way to debug this?
If the transmission is not over TLS, you can use "tcpdump".
If the transmission is over TLS, you can add the destination
addresses to "debug_peer_list".
https://www.postfix.org/postconf.5.html#debug_peer_list
Attaching a debugger or tracing system calls is definitely not what you
were looking for.
Typically when your message is rejected the bounce message will have all
the essential details you might learn from a more complete transaction
command/reply trace.
--
Viktor. 🇺🇦 Слава Україні!
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