I have a fully patched Exchange 2013 server and the latest Thunderbird IMAP-client.

When the user tries to open some subfolders under inbox he gets an error "The current operation on 'subfolder' did not succeed. The mail server for account user@Exchange responed: Server Unavailbale. 15."

Some subfolders work though and subfolders under the subfolder that cant be opened works.

I found this post but no answer to what the user changed to make it work:

https://social.technet.microsoft.com/Forums/office/en-US/2508f50f-6b28-4961-8e6c-5425914d4caa/no-server-unavailable-15-on-exchange-2013?forum=exchangesvrclients

The folder is visible and readable from other clients like Outlook and webmail.

• Edited by Harmankardon Monday, June 15, 2015 10:12 AM

Found a workaround for the problem for one user

If the user copied the mail (via another client or webmail) to another folder and then removed the old folder. Recreated it and then moved the mail back he could see the mail in the folder again.

• Marked as answer by Harmankardon Monday, June 15, 2015 10:15 AM
• Unmarked as answer by Harmankardon 20 hours 53 minutes ago
• Edited by Harmankardon 20 hours 53 minutes ago

Found another user who hase the problem with the inbox and you cant really remove the inbox folder.

Anyone that knows about a solution to this problem?

If I connect Outlook via IMAP to the same account I get another error:

Error synchronizing folder
[8004DF03-0-0-560]

And  the folder shows up empty

Hi,

According to your post, I understand that IMAP account cannot sync message with error 8004DF03-0-0-560.
If I misunderstand your concern, please do not hesitate to let me know.

Which Outlook version are you used? please upgrade to latest version for testing. Also, ensure all IMAP account or some special user face this issue.
Firstly, please ensure the configuration for IMAP client. Please refer to:
https://support.microsoft.com/en-us/kb/286197
Secondly, run Get-IMAPSettings -Server CAS1 | FL get settings for Exchange server, especially port setting. Meanwhile, ensure open the relevant port in firewall.

Meanwhile, use Microsoft Remote Connectivity Analyzer to check the IMAP mail.
Please post detail error message for further troubleshooting.

Thanks