[Exim] SMTP command timeout error.

I am running exim 3.3x and I am getting a SMTP command timeout on connection
error on incoming messages. This only appears to happen if the sender
address does not contain an @ symbol in the address. E.G. user@???
works but mx2.mail.yahoo.com does not. Any ideas on what could be causing
this.

Don Hammer
Network Administrator
Evanite Fiber Corporation
1115 SE Crystal Lake Dr
Corvallis, OR 97333
(541) 753-0391 voice
(541) 753-0388 fax
hammerd@???