Really Crazy SMTP Problem

[Michael Collette]

Eric,

Not knowing what all you've got configured exactly, here's a couple of 
possible guesses to weed out the basics.

Can you do a reverse DNS lookup on your mail server?  In other words, perform 
a whois on the IP address and get a legit domain name.  Many servers require 
this in order to keep out obvious spammers.

You should also triple check and make sure that you have SMTP open to come 
back to you from the outside world.  SMTP requires open ports coming in as 
well as going out.  Check your TCP Wrappers and whether or not IPFW or 
IPFilters is in the mix.

Later on,

Eric Harrison wrote:

> Hi,  I've been trying everything I can think of to locate the source of
> this
> problem and I finally gave up and need some help.  This is the situation:
> 
> I have a server running FreeBSD 4.7-RELEASE.  I installed Postfix on the
> machine like I have done at least 20 other times on different machines and
> got everything configured like it should be.  I noticed quickly that it
> wasn't delivering mail to any remote mail servers so I checked my mail
> queue and discovered that most of the servers were either refusing the
> connection
> or not responding.  This was a little strange so I spent about a day
> checking the postfix configuration, assuming I had just messed something
> up.
> 
> I finally came to the conclusion that everything was configured properly
> and
> then had the bright idea  to try to manually connect to the external mail
> servers to see if I could connect.  This is where it gets wierd.
> 
> $telnet smtp.ADDRESSWITHHELD.com 25
> Trying xxx.xxx.xxx.x...
> telnet: connect to address xxx.xxx.xxx.x: Connection refused
> telnet: Unable to connect to remote host
> 
> I thought this to be rather odd, but thought the worst had happened and I
> had somehow gotten a blacklisted IP (possibly used previously by a Spammer
> or something).
> 
> So I tried a server I knew to NOT be running any type of blacklist
> filtering (one of my other servers that I knew the config on) and had the
> SAME result.
> Connection refused.  The other machines on the network running mail
> servers seem to not be having any problems like this, and I talked to my
> host to see if anything was reported, and he claiimed it was a
> misconfiguration of my
> mail server.  Knowing this not to be the case, I am stumped.
> 
> If ANYONE has any information or insight, you would be a lifesaver.
> 
> Thanks,
> 
> Eric Harrison

-- 
"In theory, there is no difference between theory and practice.
In practice, there is."
- Yogi Berra