I had a RedHat 7.3 installation working properly, both sending and receiving mail with sendmail. I wanted a clean Fedora install, and since then I can send, but not receive mail.
I have modified /etc/mail/sendmail.mc and commented out the line
dnl # DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl
then ran make -C /etc/mail and restarted sendmail with service sendmail restart.
I also modified /etc/mail/access and added localhost.localdomain RELAY localhost RELAY 127.0.0.1 RELAY myserver.mydomain.org RELAY then restarted sendmail.
I have a 4 port linksys as a router/firewall between my cable modem and my server (and 2 other PCs). Port forwarding is enabled on the linksys to allow http traffic, and smtp on port 25 to be forwarded to the server - which was all working correctly before the Fedora install.
I ran ethereal and watched connections, not that I understand much of the packet info. I see connection attempts, but external mail servers never complete a connection. The typical pattern seems to be a remote server sends a SYN on port 25, I reply with SYN,ACK. Remote sends a SYN, I send 2 SYN,ACKs. Remote sends a SYN, and I send 3 SYN,ACKs, and eventualy the rmote gives up.
From any PC inside my network I can telnet to the server on port 25 andissue basic smtp instructions. I can do the same locally with 127.0.0.1 e.g.
# telnet myserver.mydomain.org 25
Trying 192.168.1.12...
Connected to myserver.mydomain.org.
Escape character is '^]'.
220 myserver.mydomain.org ESMTP Sendmail 8.12.10/8.12.10; Sun, 28 Mar 2004 11:41:01 -0500
mail from: someone@xxxxxxx
250 2.1.0 someone@xxxxxxxxxx Sender ok
rcpt to: homer
250 2.1.5 homer... Recipient ok
data
354 Enter mail, end with "." on a line by itself
Subject: test message
this is a test
