[SA-exim] Sender verify failed - need to allow particular mail in

[Debbie D]

One of my hosted clients is receiving efax's that does not come FROM a 
verified address. These mails are getting trashed as unverified sender

2007-04-26 22:37:35 H=(spserver2.kwcharlotte.local) [66.255.39.113] sender 
verify fail for <postmaster at fax>: unrouteable mail domain "fax"
2007-04-26 22:37:35 H=(spserver2.kwcharlotte.local) [66.255.39.113] 
F=<postmaster at fax> rejected RCPT <mb at bannett.net>: Sender verify failed


How can I edit exim config to allow this one through with out turning off 
the sender verify feature??

FC4
Exim 4.63
SpamAssassin 3.1.8
on a Cpanel box

thanks