FTPs unable to remove portnumber

Hello,

Our customer uses FTPS to transfer files. The configuration tells that no port is used to transfer.
When we use the GUI version of WinSCP we cannot skip the port number nor we can leave it blank.
How can we setup this connection in the GUI?

That's nonsense. You always connect to a port, when connecting over Internet (for whatever reason, FTP or not).

Maybe they mean that you use should use the default port? What is the exact wording of the instructions you were given?

Issue solved! Customer mistake.