CFExchangemail Error - Appointment cannot be cast as EmailMessage

We have a scheduled task that runs periodically to "harvest" emails out of an Exchange inbox.  It has run well for quite a while.  Recently we're getting this error:

microsoft.exchange.webservices.data.Appointment cannot be cast to microsoft.exchange.webservices.data.EmailMessage

The error appears to be getting generated within the CFExchangemail tag, itself.  Our guess is that something in the inbox is cast as an Appointment rather than mail but in looking directly at the Inbox on exchange we see nothing amiss.  We've cleared out the whole inbox and calendar of this account but the error continues.

This appears to only affect the Inbox.  I can query other folders using CFExchange with no problems.

Any ideas?

Here's the tag call where the error occurs (nothing special):

<cfexchangemail

    action = "get"

    name = "FindAccountMail"

    connection = "cxn">

    <cfexchangefilter name="Folder" value="Inbox">

    <cfexchangefilter name="MessageType" value="Mail">

</cfexchangemail>