Alias and IIS OWA

2 questions here. First, how do I set a mailbox to forward to an external address? I must be overlooking something cause I’ve tried everything I can think of. Second, my internal OWA works fine, but for my laptops when they’re off site the cann’t connect to the server. DNS resolves the name correctly, and both http and https ports are open, is there something I’m missing?
Thanks much everyone.