Stalwart Mail
Homepage: https://stalw.art/
Stalwart is a scalable, secure and robust open-source mail server software designed for the 21st century.
Usage
Set stalwart_enabled: true
in your inventories/<your_inventory>/group_vars/nas.yml
file.
Stalwart web interface can be found at http://ansible_nas_host_or_ip:8149.