Shared Hosting: We do not block any ports.
VPS Hosting: We block port 25 outbound, which we may be able to open upon request in a support ticket
Dedicated Servers: We block ports 17, 19, 1900, 53413, and 11211. We are unable to open these ports upon request.
If a port is showing as closed or filtered, in our experience, it is usually because no application or service has been configured to listen on said port.