Problem
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,
MessageRemoved
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
In tests we found huge performance issues processing large messages. If you are have occasional messages that won't process with IMAP, check your mailbox for large messages, its possible they are not able to be downloaded in time, in order to meet mailserver timeouts, or JIRA timeouts. POP is a much better performing protocol for JIRA usage, as mail handlers require ALL the mail ALL the time, the IMAP 'features' for extracting bits of the message separately are clever but not required here.
Solution
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