UID Error Message - IMAP Email

Issue

When reading email in a third-party mail client (e.g. Outlook, Thunderbird, etc), a pop-up occurs 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: depends on service provider, e.g. imap.hyperoffice.us
Port: 143
Error Code: 0x800CCCDB

Explanation

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

Workaround

Navigate away from that folder in the browser or the third-party mail client. It is advised to only access mail through one method at a time.