Thanks! I spent quite some time on your site and am impressed, especially with your transparency as founder. One suggestion: it is clear the content is not written by a native English speaker. At first this created doubts for me, it just feels less professional.
Suggest you hire an editor to fix up your content… or contact me and I’ll do it for free.
Also, improvmx.com is a great product as well.
If you like open source, https://maddy.email/ is a single binary deployment that can handle everything even IMAP.
https://mailcow.github.io/mailcow-dockerized-docs/ is a dockerize solution with super detail document as well.