I have a noob problem with sendmail (or dhcpd) on firewall machine. When I do "telnet 0 smtp" or "telnet external_address smtp" then all is fine, I get 220 prompt, but when I do "telnet internal_address smtp" then sendmail tries to resolve internal IP address, and 220 prompt shows up after a minute or so. The question probably is how to tell sendmail not to verify the whole internal network? I can fill up the hosts file, but that's hardly a solution, since internal IP addresses are dynamically allocated with dhcp server. The funny thing is, this smtp delivery failure started to happen today, everything worked well before.