Issue

When reading email in your 3rd-party mail client (eg Outlook, Thunderbird, etc), you sporadically receive a pop-up stating:

"The UID of a message changed unexpectedly.  This typically indicates a server bug.  Your program may not function properly after this."

MsgSeqNum 000: Previous UID: 12345678, New UID: 12345789.
Protocol: IMAP
Server: imap.HyperOffice.com
Port: 143
Error Code: 0x800CCCDB

Explanation

This error occurs when you have both an IMAP connection open to a specific folder and also a WebMail session open looking at that same folder.  This is a known issue with the IMAP protocol.

Workaround

Navigate away from that folder in your browser or your 3rd-party mail client.  It is advised that you only access your mail through only one method at a time.