How do I configure the IMAP host on Open-Xchange?
By default, the Open-Xchange server sets up the IMAP server host to be localhost or 127.0.0.1, which cannot be reachable from outside.
The configuration in Open-Xchange must be updated to specify the host on which the IMAP server is running.
If the IMAP server is set up on the same server as Open-Xchange, then the database entry must be updated to specify the host address of the Open-Xchange server.
If the IMAP server is located on a different server than the Open-Xchange server, then the IMAP address and port needs to be updated in the Open-Xchange server's database to point to the IMAP host and port. The Email Configuration with IMAP properties are outlined in this article: Open-Xchange IMAP configuration.