[Exim] Dealing with retarded mail software

Hi,

I have been trying to find a solution for this problem for a while now and have drawn a blank. One of the ISP's I consult for has a billing system called Prism. Prism sends out bills via email. Occasionally somebody will enter a malformed address into a customers billing details. When Prism does it's billing run and tries to send to that malformed address, Exim (quite correctly) returns a "501 domain missing or malformed", at which point Prism's billing run just stops and sits there looking dumb (not quite so clever!). Using SMTP rewrite rules and strip_trailing_dot I have gotten around some of the bad addresses but it's not possible to consider every possible way that the staff may enter email addresses incorrectly. What I would like to be able to do is to accept a malformed address and it's mail and then bounce it after that as an undeliverable/unrouteable address, instead of at RCPT time. I cannot find a way to do this (apart from hacking at Exim's source which I really don't feel comfortable with) and would really appreciate either some assistance in this or a confirmation that it can't be done.


Thanks


Clint