We would like to be transparent about our technology. Many parts of our stack are open-source components.
Custom software is primarily developed in dlang. Dlang provides static typing, memory safety, quick compilation, easily readable code and build-in unit tests. We find it enables us to quickly write effective code in a straightforward manner.
The custom SMTP and POP daemon is written in dlang using the vibe.d framework. Vibe.d provides an easy-to-use set of tools for web development using an asynchronous I/O model without the drawbacks of callback functions. It has extensive functionality and we have been pleasently suprised by the friendly support provided by it's main developer, Sönke Ludwig.
Encryption is done using the openSSL and secureD libraries.
We use Hetzner in Germany as our primary infrastructure provider.
It would further improve security to move to our own servers with control over firmware, any CPU or server remote management software, hyperthreading settings and virtual machine technology. We are aware of this being detrimental to security but has chosen to put the move on hold for now while focussing on stabilizing our software stack.
Other areas of security and privacy improvements are
Other areas of improvements are
Now go mail someone!