Two Exchange servers one Public IP

So I have two Exchange servers in my office. One has been working forever no worries.

 I just moved a second one in a couple of days ago. (it will be in my office for about 2 months)

The second server need to be able to send receive and connect to the OWA and Smart phones and connect to offsite outlook of course,

I have changed the second server to receive mail on port 26 then on my router I have told all traffic from port 26 ->  to change to port 25 on the second IP.

So I can send and receive emails no worries. The next issue is I need OWA access to work. This runs on port 443.

The existing server is of course already using this port.

What can I do.

I can;t get a second public IP as my router does not allow this.
A second internet connection is possible if I have no choice.