[Exim] unwanted mutiple emails

Can anyone help?

I have recently been given the administration of a server running Red
Hat 7.1 with Exim 3.33 behind a CISCO Secure PIX firewall version
5.3(1). I am currently having problems with a few customers who are
reciving the same emails over 200 times a day. This has been going on
now for over a week now and I have tried everything I can but with
little luck. On customer has received over 900 copies of the same
mesage in one week from a mailing list.

I thought it was an smtp problem and so under the Transports
configuration section I had

remote_smtp
driver = smtp
connect_timeout = 5m
command_timeout = 5m
data_timeout = 7m
final_timeout = 10m

two days later and the problem is still there. Can anyone put me in the
right direction.

--

Regards

Diye Wariebi