Postfix Installation Update apt apt update Get packages postfix and mailutils apt install postfix mailutils Install postfix - Configuration window sudo apt install postfix Reconfigure postfix via configuration window sudo dpkg-reconfigure postfix Settings Relay / Smarthost Test localhost Telnet to localhost telnet 127.0.0.1 25 Trying 127.0.0.1... Connected to 127.0.0.1. Escape character is '^]'. 220 subdomain.domain.tlg ESMTP Postfix (Debian/GNU)