Microsoft finally published access to Office 365 IMAP server using OAuth 2.0 authentication. We had to enable a workaround for it that we had made for other Microsoft IMAP server on Outlook.com.
Another related forum thread on this issue can be found here: https://forum.rebex.net/12653/does-rebex-support-office-mailbox-using-imap-with-oauth-token
Trial hotfix version that makes it possible to connect to Office 365 IMAP server can be downloaded here:
Full version of this hotfix is for available for paying customers at email@example.com as part of their support contract.
This workaround will be available in the next release of our components.