Mail services

Sending email from one person to another over a network or the Internet requires:

  1. The sender’s email client (Mail User Agent) sends the message.

  2. One or more Mail Transfer Agents (MTA) to transfer the message.

  3. The final MTA sends the message to a Mail Delivery Agent (MDA) for delivery to the recipient’s inbox.

  4. Finally, the recipient’s email client retrieves the message, usually via a POP3 or IMAP server.

These systems must all be configured correctly to successfully deliver a message.

Mail User Agent

Thunderbird is the default Mail User Agent (email client) used by Ubuntu. It comes pre-installed on all Ubuntu machines from Ubuntu 16.04 LTS (Xenial) onwards.

If you need to install Thunderbird manually, this short guide will walk you through the steps.

Mail Transfer Agent

On Ubuntu, Postfix is the default supported MTA. It is compatible with the sendmail MTA.

  • Install Postfix explains how to install and configure Postfix, including how to configure SMTP for secure communications.

Exim4 can be installed in place of sendmail, although its configuration is quite different.

  • Install Exim4 explains how to install and configure Exim4 on Ubuntu.

Mail Delivery Agent

Dovecot is an MDA written with security primarily in mind. It supports the mbox and Maildir mailbox formats.