sSMTP, this mailing list, and helo errors

[Michael Powell]

Chad Perrin wrote:

> I moved email from a FreeBSD 6.2 machine to a FreeBSD 7.2 machine.
> 
> On both machines, I'm using sSMTP[1] to send email to a mailserver
> managed by a shared hosting server, with SSL/TLS authentication.
> Everything works, except for one "small" problem -- sending email to this
> list.  It has apparently exposed a problem with the setup.  I get a "Helo
> command rejected: Host not found" error when sending to this list.
> 
> The weird part is that I'm using *exactly* the same ssmtp.conf file on
> both the 7.2 system and the 6.2 system.  As you can see -- since this
> email comes from the 6.2 system -- that configuration file isn't causing
> any problems sending with sSMTP on 6.2, so I'm a little confused about
> the cause of the problem.  Where else should I look for a problem?
> 

My first guess would be DNS. Whenever I see something like a 'host not 
found' of this nature I think "no PTR record". Although I would think wrt 
mail the MX record would matter. My thinking is the two configs you have 
mentioned being identical the problem is a third config somewhere else, and 
first thing I'd look at is name resolution, forward and reverse.

Grab a copy of the transaction with tcpdump or Wireshark. Perhaps the list 
filtering software is seeing mail with a From: <some domain> it isn't 
recognizing and blocking. Tcpdump/Wireshark from both hosts and compare for 
differences in the mail headers, e.g., the one that works and the one that 
doesn't. With Wireshark this is easy, just start a capture, send an email, 
stop capture, and use the "Follow TCP Stream" menu option. Or use tcpdump 
and import it into Wireshark.

-Mike