[Exim] how to say "never THIS message"

I have noted that some MTA reply with
550: explain
and explain say that the file did contain a virus and so is not
accepted. an unknown MTA so consider it as a "Used does not
accept any email from me" and so stop sending to that address.
What is exactly the code (issued after receiving the message)
for "I cannot accept now THIS message, and i won't ever accept IT,
so do not retry, but you can freely try to send any other message "
?


--
Leonardo Boselli
Nucleo informatico e Telematico
Dipartimento Ingegneria Civile
Universita` di Firenze
Via Santa Marta 3
I-50139 Firenze
+39 055-4796-431
+39 348-8605-348
fax 055-495-333