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You occasionally have messages that won't process, and are using an IMAP mail server.
Folder Closed / Repeat Processing
IMAP is touted as a more advanced protocol than POP, which is true in some regards, but in some scenarios it can be problematic (see link below). If you experience FolderClosedExceptions,
Message Removed
If you have concurrent access to a common mailbox its possible that a message may be 'removed' by another handler process, the error is likely to be harmless, unless the configuration caused the message to be dropped.
Performance Issues
We have found that there can be significant performance problems with IMAP when it is dealing with large messages. Take a look at our test results for more information.
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