Caddy on Linux: web server with automatic HTTPS
Install Caddy on Ubuntu and Debian via the official repository and put sites and applications behind automatic HTTPS, with reverse proxy, load balancing, PHP, Docker, and plugins.
tls
SSL/TLS in Postfix and Dovecot: why and how
Let's Encrypt certificate, ports 465/587/993/995, TLS 1.2 where there is a password, Dovecot 2.3 and 2.4, tests, and MTA-STS against the attack that strips STARTTLS.