Exim Mail Rejection Issue

[StealthDesign]

What is causing this person's mail to be rejected by my server and how can I fix this? He is a legit sender and his mails should not be rejected.

(Note the sender and recipient's addresses have been modified for privacy reasons.)

exim_rejectlog.1:2006-10-07 19:47:57 H=(mtiwmhc13.worldnet.att.net) [204.127.131.117] F=<[email protected]> rejected RCPT <[email protected]>: Sender verify failed

Any assistance would be greatly appreciated.
Thanks in advance.

 

[mctDarren]

Is the person relaying mail through his AT&T account for another domain? Or are they using their AT&T address?

 

[StealthDesign]

He is relaying mail for another address (an email address at his own domain).

 

[nickp666]

do you have the 'Use callouts to verify the existance of e-mail senders' box checked in the exim configuration editor in WHM?

if so turn it off and it should work

 

[StealthDesign]

Thanks, I gave that a try and it seems to work now.