webmail / usermin not working

When I try and access webmail.my_domain.com nothing is loaded/displayed do I need to enable something to get this to work/is it using any special port numbers etc?

Normally, accessing webmail.domain.tld would redirect to port 20000, where Usermin resides.

Does it work if you access Usermin directly, using your IP address? You can try something like this:

https://your.ip.address:20000

Apologies please ignore this, port 20000 was blocked by our local firewall, unblocked it and it is working fine, thanks

Actually one other related question, can we stop the automatic SSL https connection being triggered can we use none SSL https to access usermin if so how do we do this?