netstat -pant|grep ":25"|grep LISTEN to see if any program is listening... output should look like: tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 21493/sendmail
guess it'll say 'postfix' or 'master' instead of 'sendmail' on RH6.
]# netstat -pant|grep ":25"|grep LISTEN tcp 0 0 209.216.9.56:25 0.0.0.0:* LISTEN 14058/master tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 14058/master
How long are you waiting for a response to appear? Mailers do an assortment of reverse-dns lookups and perhaps an ident query to the source before responding. If you firewall these with a 'drop' instead of 'reject' you leave the application hanging for fairly long timeout. And some mailers have a config option for an intentional delay before their first message and will drop the connection it the other end sends first (snmp protocol requires the connecting host to wait). Also, you should have something showing up in /var/log/mailllog about the connections.
I can't find anything in there that corresponds to the attempt to send an email. And why would I when there is no communication from the server in my telnet session? The problem appears to be in telnet, not in postfix. Again, this is one of 3 examples of my telnet sessions from 2 emails ago:
[root@mydomain john]# telnet 127.0.0.1 25 Trying 127.0.0.1... Connected to 127.0.0.1. Escape character is '^]'. HELO justtesting MAIL FROM: testing@gmail.com RCPT TO: testing@gmail.com DATA To: testing@gmail.com From: testing@gmail.com Subject: testing Date: Tu, Oct 2012 10:21:11 -0500 Testing . QUIT
Then it hangs. I never get back to a command prompt. There is never any interaction with the telnet program after the initial response. How do I trouble-shoot this? TIA, John