From wiki

Sending emails is important for a server. It allows it to notify you of various events (update pending, task failure, breach attempt…).

This guide will show you two different configuration options:

  • Send only: Simple configuration. The server uses an external SMTP server to send emails. Use this if you want to just receive notification emails from a server.
  • Complete: A complete email infrastructure with your own SMTP and IMAP server.Including a webmail, a spam filter and an antivirus.