|First, unless you have set it up to where you are using 128-bit SSL, then there is no need to use the https:// prefix. You have to set up a certificate authority or use a third party issuer to do that.|
The proper syntax for a default OWA server would be:
For 128-bit SSL:
If these do not work, you are probably not typing the exact FQDN of your internal server, or that server does not have the public LAN atttribute through your firewall.
Allow public access through port 443 to your servers IP address if you have SSL security enabled on it. I do not recommend doing this if you do not have a security certificate enabled on it.
Either way, the internet has to have port accesst to this server for it work.