backup config to FTP with custom port number

Configuring Sophos Firewall to back up config file to FTP server. Settings page has a field for the FTP server IP, but there seems to be no way to specify the port number. My FTP server was using Port 21, and this worked fine, so I assume that Sophos OS uses Port 21 by default. But now, due to new security policies, the FTP server is using a different port number. I can't see how to get the Sophos OS to use the new port number when doing the backups. 

Added FR TAG
[edited by: Erick Jan at 7:32 AM (GMT -8) on 29 Feb 2024]