IMAP test, error "311: x0001 NO Server Unavailable. 15&

[JonD]

I want to count messages in Inbox by IMAP4 protocol.


But as result I have the good and error reply:


How to fix it?

You can see login in this format: <NetBIOS_domain_name>\<SamAccountName>\<Shared_mailbox>. Mailbox is hosted on Exchange Server 2016.

[KS-Soft]

1) There are about 200 versions of HostMonitor. Which one do you use?

2) Why do you think this is bug?
If you think Exchange does not return such error to HostMonitor, you may check network packets using some analyzer, e.g WireShark.
I think Exchange server may return such error for various reasons. You should check Exchange logs and Microsoft tech manuals/forums.

E.g.
If there are other connection at the same time (e.g. other tests) you may try to increase "maximum connections from a single user" Exchange option.

In other cases enabling IMAP protocol logging helps to fix such errors
>Set-ImapSettings -Server <servername> -ProtocolLogEnabled $true
Please don't ask us why, ask Microsoft

Regards
Alex