Modoboa is a nice all-in-one email package. Sadly it lacks configuration possibilities for certificates and the default config uses just self signed certificates. This tutorial explains how to create and configure lets encrypt for your mail server.

I will explain and provide some scripts how you can setup a Windows Remote Desktop Server behind a NAT (even on IPv6 DSLight connections). But there is a drawback: You need a public Linux server. Although low budget vm-solutions (e.g. DigitalOcean) start at about 5 USD.