I run sendmail-8.12.11-4.6 on Fedora Core 2. I have recently changed from a dialup connection to a VSAT link but my email is still hosted by the dialup provider whose smtp server cannot accept my mail now. I consequently removed their server from my SMART_HOST entry. All is well and mail goes out but some of my mail is rejected due to some problem with my public IP. My new provider, in response has given me an smtp server to route my email but the trouble is, how do I incorporate a server that requires authentication? the entry in my sendmail.cf was just DSmail.mydialupisp.com but I gues that wont work as it is because now I have a username and password for the outgoing smtp server. Kindly help.

The following link should help you resolve your problem:
http://www.infohiiway.com/sendmail/#four

my first try did not work, still trying

Yes this has finally worked. Thanks scowles.