Just a shot in the dark, but do you have greetpause set to something above 20 seconds?
That could explain why you can telnet to port 25 just fine, but the sender daemon (a lot of the php mailers for example) may not wait long enough.
Telnet to port 25 and don't hit a key until you get something like this:
220 {hostname} ESMTP Sendmail 8.14.4/8.14.4/
- Bryan Bradsby
Postmaster 512.936.2248 Texas State Government Network
On Fri, 2010-07-09 at 15:01 -0400, Dennis Clarke wrote:
Well that tells me dovecot is working fine but sendmail is not listening to roaming mail clients.
Sending of message failed. The message could not be sent because connecting to SMTP server foo.domainname.ca failed. The server may be unavailable or is refusing SMTP connections. Please verify that your SMTP server settings are correct and try again, or contact the server administrator.
However I can telnet to the port 25 just fine ... bizarre.