[Cialug] Qwest subtly filtering port 25

[Tim Perdue]

Not sure if anyone else ran into this, but it had me vexed all week. I 
have used thunderbird for years from home to relay off an outside server 
and it just quit working and starting giving an error about SMTP timeout.

Turns out Qwest has done some sort of subtle blocking of port 25 that 
causes SMTP to timeout, although the port appears to be open (you can 
telnet to it).

http://mikedopp.com/2011/bold-move-from-qwest-to-block-port-25-traffic/

A call to tech support got them to drop the filtering within a few 
minutes and my email works again.