We are running a number of Exchange 5.5 servers, acting as
bridge-heads. They are divide between two physical
locations (call them A & B), but reside within a single
Exchange 'site'.

To provide resiliance, external sites have two X.400
connectors, one to A with cost 1 and one to B cost 100 (or
vice versa). All other settings, e.g. Override, are the
same.

This all works well, however, we are finding that mail
begins to queue on the higher cost connectors from time to
time (even though no network or service outagages), and
will not go over to the lower cost server unless an MTA
restart is carried out (which being a 24/7 service is v.
inconvenient).

Does anybody know why this is happening and more
importantly, how to stop it from occuring in the first
place.