Hi @MK-19991,
Before we go on, would you mind clarifying the detailed build number of your Exchange 2010 and on which mail client you are trying to configuring the Exchange account via IMAP?
Besides, please refer to the document below and make sure IMAP service has been enabled and is running properly:
Enable IMAP4 in Exchange 2010
Furthermore, as regards to the error message you shared above, I tried searching further and found the following thread which mentions a similar error but involves PHP and a third party application:
Inbound Email: PHP Notice: Unknown: Kerberos error report emails with MS Exchange
(Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.)
Sorry that I personally am not familar with either that software or PHP, but considering that the error message is similar to what you encountered, I'd recommend having a look at the discussion there and see if the provided solution can apply to your situation.
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