[Exim] Unexpected disconnection?

Hi
This problem has been plagueing me for a while

When run normally (ie from MUA's) exim works fine

However when I try to run any of several scripts usig perl modules
Net::SMTP and MIME::Entity I get the above error

When I run exim -d9 -db I get

unexpected disconnection while reading SMTP data from
localhost.localdomain [127.0.0.1]
SMTP>> 421 Lost incoming connection
This is after setting up a dummy server on localhost so this would seem
to rule out network problems

This same problem occurs running RH7/kernel 2.4.1/exim-3.15 and
RH7.1/exim3.22

Any help would be greatly appreciated