[Exim] SMTP connection from [219.137.157.183] lost ?

Hi All.

Having severe problems here with Exim 3.33 running on RedHat 8.2
where very few people can actually send mail through us. This has only
just started happening in the last few days and I appear to be getting
around
30 - 40 connections where the connection is just lost. I've tried hunting
around
and found a few references to this problem but mostly dating from around
1999 and none of the suggested solutions worked.

Any ideas on what I can do to trace/fix the problem would be very much
appreciated. Upgrading is not an option unfortunately, tried that and
failed misserably :( My home office box running 3.33 is working fine and
I just can't see any difference between them. No recent changes to the
config, no changes to the box, no software updates to affect it. Everything
else is working fine, MySql, Apache, Bind, Ftp etc. etc. just mail. Plenty
of memory free, plenty of disk space, checked permissions on directories
etc. etc.

Any ideas would be very much appreciated.

Ken.