Mechanism specific option
When using the rimap mechanism, this option describes the remote server to forward authentication requests to.
Hostname can be a hostname (imap.example.com) or an IP address (192.168.0.1).
The remote host is contacted on the imap service port. A non-default port can be specified by appending a slash and the port name or number to the hostname argument (192.168.0.1/14343).

Another mechanisms may use some config files that should be set up with this option.