I have a Linux firewall/mailserver running kernel 2.4.10 and sendmail 8.12.1. There are a few domains that I cannot send mail to from the firewall. However - if I try to send mail from an internal box, mail flows to the same domain just fine. The firewall is NAT'ing using the external interface's IP address, so both IPs being seen by the destination server are the same.
Telnetting to port 25 on the destination server simply hangs on the "Trying...", no connection is ever made (left it for nearly 30 minutes one time). All of that was telnetting from the firewall.
Telnetting from any machine (Linux, XP and 98) all connect to port 25 just fine. I issued a "HELO" and got back a successful reply -- didn't want to go much further without talking to the admin of their network...
Any ideas? Things that came to my mind that I have ruled out are ident lookup that I drop at the firewall - however, no packets are violating that firewall rule -- also a sniff showed nothing being returned to my firewall from the destination mailserver.
The other thing I was thinking of was a reverse DNS problem. My reverse DNS is different than my sending domain (ie @home reverse and a standard domain for the mail source domain). But I can connect just fine from an internal box...
Anyway, thanks in advance,
Paul
Telnetting to port 25 on the destination server simply hangs on the "Trying...", no connection is ever made (left it for nearly 30 minutes one time). All of that was telnetting from the firewall.
Telnetting from any machine (Linux, XP and 98) all connect to port 25 just fine. I issued a "HELO" and got back a successful reply -- didn't want to go much further without talking to the admin of their network...
Any ideas? Things that came to my mind that I have ruled out are ident lookup that I drop at the firewall - however, no packets are violating that firewall rule -- also a sniff showed nothing being returned to my firewall from the destination mailserver.
The other thing I was thinking of was a reverse DNS problem. My reverse DNS is different than my sending domain (ie @home reverse and a standard domain for the mail source domain). But I can connect just fine from an internal box...
Anyway, thanks in advance,
Paul
