Matt,
Thanks for the response. <maxLoadedSpoolMessages> was set to 50000.
For grins and giggles I set it to 2000 (also in the mailConfig_bak.xml) and restarted the Spool but it didn't resolve anything. The service just reset it back to the default 50000, so I'll have to stop SM, make the change, and restart it (as I can't stop/start the SmarterMail service atm will have to wait until 1-2am to give that a try).
We only have 21 messages that s/b in the All Messages queue with 3 Waiting to Deliver, and 955 messages in Virus Quarantine. So, it is well under the 50000 limit anyway.