Sendmail & MailScanner - can't connect from public addresses

[Jason Williams]

>
>Finished setting up the latest MailScanner and Sendmail, however, although I
>can connect to the mail server via telnet to port 25 from any machine on the
>local subnet, it does not respond from any request from public IP addresses.
>There is no firewall on this server, but it is behind a firewall. Nmap shows
>port 25 as open.  When I open port forwarding from two other firewalls (from
>different ISP address ranges) to the mail server, I get no response when
>telnetting from the public side to the smtp port. (It is not the firewall
>since port forwarding works to the other mail servers)

When you say that NMAP shows port 25 open, are you doing the scan from the
inside or outside?

My initial thought is that although port 25 is open, the firewall is
blocking all attempts to your mail server on port 25.
What OS and firewall are you running if you dont mind me asking.

>It appears that either Sendmail or MailScanner is only accepting connections
>from the local subnet.

If it's accepting connections from the inside, that means it's setup
correctly as a MTA, which leads me to believe the firewall is where the
problem is. If you were unable to connect at all from the inside, then
that's another story.

Have you tried turning up the logging on sendmail? Do you see any
interesting entries in your firewall log when trying to access your server
from the outside?

- Jason