You're not using a current version of MFCMAPI. That extra "Size" field is a bug: https://mfcmapi.codeplex.com/workitem/15765. That column is really the message flags property. and it looks like you're really interested in one of the flags, MSGFLAG_UNSENT, contained in that property. You might be able to write an OOM script that looks at that property to do your filtering.
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