This is a simple virtual user management system for OpenSMTPD and
Dovecot, as explained on my blog [post] (or [over gemini])
It won't work out-of-the-box. Before starting using it, you need to
provide a valid `userdb` file (as explained in the blog post, a sample
is included in the repo), and possibly fix `userctl.awk` to define
your `vmail` user (the UNIX user that will accept the mail for your
users) and the path for the maildir on the disk.