backupexec fails every morning due to spam

veritas backupexec 9.1 has been running fine without a problem and then recently has been failing every night due to one use who has spam email that disrupts it.  This is a sample of the error message.   When I look at his mailbox, I see these in use items in his deleted mail folder. I don't know why backupexec states they are in use?  I'm sure my backups are still valid, I just don't like seeing the failed message every morning....any suggestions?  thanks

 

Backup - \\EX01\Microsoft Exchange Mailboxes The item \\EX01\Microsoft Exchange Mailboxes\Tania Daran [tdaran]?Top of Information Store?Inbox????????????????????????????????????????????????????????????????????????Microsoft Office 2007 ready to download in use - skipped.
The item \\EX01\Microsoft Exchange Mailboxes\Tania Daran [tdaran]?Top of Information Store?Inbox????????????????????????????????????????????????????????????????????????Free Telephone calling plan in use - skipped.