What is a Mail Transfer Agent (MTA) or Relay in SMTP? (Email Smtp Server)


A mail transfer agent or MTA 1) is a SMTP server that receives an email and transmits it to its final destination, the Mail Delivery Agent SMTP server.

MTA is also known as:

  • message transfer agent.
  • or SMTP relay


If you want to know the base of email, see this page: How does the email system work? SMTP, POP, IMAP explained

Transport / Transmission

An MTA may transport the E-Mail messages:

Transport Type Description
remotely to another server MTA
locally to the Local Delivery Agent (MDA/LDA (that write them into the mailbox)



The well-known MTA that you would install on your server are:


Client MUAs (such as mutt, thunderbird, sylpheed, evolution, kmail) hand off newly sent messages to an MTA. 2)

Discover More
Email - Mail User Agent (MUA) - Mail Client

A Mail User Agent (MUA) is the technical term from a email client application. User agentMail User Agent (MUA)user applicationuser agent on the web A MUA can: read and write in the mailbox and...
Email - Mailbox

A mailbox is a file where the emails message are stored. A user application (known as MUA) can read and write a mailbox The Mail Delivery Agent will write the email received by the SMTP server (MTA)...
Email - Mille and one way to send an email (professional and user)

This article shows you Mille and one way to send an email (ie known as transport in SMTP. submission port Before continuing, you need to know the basics of email and how it works with SMTP. If you...
Email - Postfix

Postfix is a SMTP server, supporting LDAP, SMTP AUTH (SASL), TLS The postfix installation installs also an alias to the sendmail command line. Doc - the SMTP...
Email - on Linux

Linux runs a “locally configured” mailer daemon that doesn't route messages by default through the Internet but only copies messages to other users spool directories It is real SMTP-compliant email,...

FetchMail is an application which: retrieves email from remote servers (via POP3 and IMAP) and : delivers it to the local Smtp Server (MTA) or forward them if necessary to another Smtp Server...
How does the email system work? SMTP, POP, IMAP explained

This page gives you the foundations of the email system. At the end, you should be able to understand why when you configure your email client, you need to set up: The SMTP configuration And the...
Dkim Record Text Format Ovh Dns Zone
How to configure DKIM with PostFix, a step by step guide

This article will show and explain you how to install DKIM with OpenDkim as a milter for Postix on CentOS
The SMTP Protocol

A summary of what the SMTP protocol is and how to send an email from a network connection with telnet or netcat

Share this page:
Follow us:
Task Runner