[Exim] Exiscan using reject behaviour

All.

I'm just playing with the av part of exiscan at the moment using sophos
sweep as a command line scanner. I have the action set to reject.

I've tested it with a number of e-mail clients - namely execmail,
Outlook, imp (webmail) and Netscape. Exim and exiscan behave properly
and reject messages at smtp time if viruses are present.

However the problem I have is that only Netscape actually responds to
the user in a useful way. It is the only one of the clients that I have
tested which passes on the server response to the client - i.e A useful
message such as "An error occurred while sending mail. The mail server
responded: this message contains a virus or other harmful content
(EICAR-AV-Test)."

All the other clients just give a standard response for a 5xx return
code such as "Unknown error" "Error communicating with SMTP server" etc.

I'm curious as to how other people are implementing av under exiscan in
order to provide the sender with a reasonable error message ?

TYIA.

Nigel.