The repository has only one file -- make-mta.sh, which will install
everything you need to run your own mail server.

It has been tested on Ubuntu 18.04 and 20.04 LTS, and should probably
run more or less as is on other Debian-derived systems.

It is recommended that the script is only run on a fresh,
newly-installed machine.  The testing has been done on a 2GB virtual
machine at DigitalOcean.

For a background to why this script exists, see:

https://lars.ingebrigtsen.no/2020/03/25/so-you-want-to-run-your-own-mail-server/ and
https://lars.ingebrigtsen.no/2020/07/26/so-you-want-to-run-your-own-mail-server-redux/

The script sets up an MTA with:

* exim4 with STARTTLS and DKIM
* Dovecot IMAP with TLS
* ufw firewall and fail2ban
* SPF, DMARC and MTA-STS
* Certificates for everything from Let's Encrypt