Tuesday, February 4, 2003 07:15 AM
So, can you (or any host) connect to your sendmail server (port 25)? Is the sending party able to resolve the hostname, is it in DNS? If not, can they connect by mailing to the IP address? (try "To: email@example.com" with the IP address in square brackets in place of the domain name, e.g. instead of "To: firstname.lastname@example.org")
Are they and your Sendmail server behind different firewalls?