Software :: Sendmail - Telnet Not Connecting On Port 25?

I have been trying all day today to setup a sendmail SMTP server on our Red Hat 5.5 dev box. We have 2 network cards, 1 to the local network with a 192.168 prefix and an external card which goes out to the web through a BT leased line through a Cisco router.

First I followed one of the many helpful tutorials online to setup sendmail, installed all the required packages and made a couple of small config changes to allow the service to listen on all IP addresses rather than just the localhost 127.0.0.1.

The main change is in the /etc/mail/sendmail.mc file where I have changed the following line;

DAEMON_OPTIONS(`Port=smtp,Addr=x.x.x.x, Name=MTA')dnl

I have tried removing Addr completely, setting to either the local or external IP and then rebuilding the sendmail file using 'make -C /etc/mail' and then restarting using 'service sendmail restart'

The SMTP port has been added into the firewall and it is showing to be listening on IP 0.0.0.0:25 which I believe means it is listening on all IP's assigned to the machine, sendmail is also in listen mode and running correctly.

Finally I have changed the /etc/mail/access file to include the local IP range 192.168 and external IP range and rebuilt this into the /etc/mail/access.db file and then restarted sendmail.

Googling the error all the sites I have found talk about making sure the 'DAEMON_OPTIONS(`Port=smtp,Addr=x.x.x.x, Name=MTA')dnl' line is uncommented and not much else in terms of what else might be incorrect.

I am starting to run out of ideas on things to change or check, telnet works correctly on other ports on the same server, ie httpd for apache on port 80. I have also rebooted the server to make sure that it wasn't something odd happening.