I decided that I wanted my own email. Then I decided that I wanted my own many things. Then I realized that these things were better than their proprietary alternatives, and began tailoring my site to be privacy-centric. Then I let my friends have accounts.
Here we are. katabaticat.net: If it exists, I will integrate it or self-host a superior alternative for free.
Matrix and Hubzilla accounts are open to registration for the public, however webmail is only available to people I trust. If you are my friend, you can contact me to request an account.