Debug Exchange management pack

On the server that is running Exchange, add the following registry key (type
DWORD) and set the value to 1:
HKLM/Software/Microsoft/Exchange MOM/DebugLS

Note:
Remember to set the value to 0 when you want to turn off logging.

Stop and restart the MOM service on the server that is running Exchange.
Make sure to grant the Mailbox Access Account full rights to
%systemdrive%; otherwise, nothing useful will be logged to ExMPLS_LOG.txt.
Be sure to remove the right afterward.

We may be able to find something useful. If you have already done this,
please disregard.