To the new owners: I googled mailcow, got to the web site and found nothing to explain what it is, not even in the docs. Eventually I noticed the "People also ask" section in the Google results page:
> What is Mailcow?
> fully managed by Elestio. Mailcow is a Docker-based email server, based on Dovecot, Postfix and other open-source software, that provides a modern web UI for administration.
Hopefully this is correct but who knows.