[exim] 421 Lost incoming connection

I'm running exim-4.63-5.fc6 and spamassassin 3.1.8,

I get a lot of bounced incoming mail, typical msg is:

421 Lost incoming connection

The SMTP transaction started in line 0.
The error was detected in line 3.
0 previous messages were successfully processed.
The rest of the batch was abandoned.
421 Lost incoming connection
Transaction started in line 0
Error detected in line 3

Any suggestions? I don't know if this is due to exim, sa, or some
interaction between them..
I noticed at times there are several hundred copies of exim running.

Thanks