Fax service receipt

In 2003 i’ve enabled the fax services—2 nearly identical dell servers—- one of the machines successfully sends an email receipt back to the sender and the other does not–event log reads below. Everything in the fax config is the same, does anyone have an idea why one works and the other does not? it’s killing me….
thanks

The fax service has failed to generate a positive delivery receipt using SMTP.

The following error occurred: 0x80040213.
This error code indicates the cause of the error.