[Exim] Relay Problem

Hi,
I'm new to this list so please excuse me if this is a FAQ.

I'm running Exim 3.35 with RAV anti spam/virus as a gateway for several
domains. Incoming messages with a To: field of the form

"victim@???

are being routed to victim@???

The percent hack version of this is happily rejected, but the version with
two actual @ symbols is allowed through. I've read and re-read the exim
docs, spoken with a few exim-using postmasters I know and nobody seems
able to trap these messages.

I'm getting pretty desperate now, can anyone shed any light on this?

Very many thanks,

Roy Coates.