One domain, port 80 on one server, port 443 on a second server.

First of all, this will be a temporary setup. I need http on server1 and https on server2. The AnaolgX PortMapper did the trick. I installed it on server1 and mapped 443 to server2. The new server is a Citrix gateway and the other solutions I tried resulted in SSL errors. The proxy works so far with no issues.

http://server1 -> old server
https://server1 -> new server

Server1 will be the proxy so it should have plenty of resources to handle the load.