How do I open OUTGOING ports in the firewall?

[disoft]

Hi,

I need to be able to ftp out of my plesk server to copy backups to a remote location.
With the firewall disabled, all works fine.

With the firewall enabled, ftp just hangs.

I have seen plenty of threads on how to add open incoming ports, but how do I set up outgoing ones to enable ftp to work?

many thanks in advance.