Sending Email from your Server using an MTA or Null Mailer (Mail Transport Agent)

Last Updated on September 21, 2023 EDT by Jordan

Introduction
Option 1 – Install an MTA (Mail Transport Agent)
1. Related Articles about MTA’s and SMTP on Linux
Option 2 – Install a Nullmailer (ssmtp)
1. ssmtp is No Longer Maintained
Option 3 – msmtp an alternative to ssmtp
Changelog

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Introduction

I created this article because someone asked, “How do I monitor my software raid and the associated drives? smartctl needs to be able to send email?

What is an MTA?

MTA stands for Mail Transfer Agent. It is a software application responsible for sending and receiving email messages between different servers on the internet. When you send an email, your email client communicates with the MTA on your email server, which then sends the message to the MTA on the recipient’s email server. The MTA ensures that the message is delivered to the correct destination and handles any errors or problems that may occur during transmission.

List of Popular Linux MTA’s

Postfix – http://www.postfix.org/

Sendmail – http://www.sendmail.com/
Exim – http://www.exim.org/
Qmail – http://cr.yp.to/qmail.html
Zimbra – https://www.zimbra.com/
OpenSMTPD – https://www.opensmtpd.org/
Haraka – https://github.com/haraka/Haraka
Courier – https://sourceforge.net/projects/courier/

What is Nullmailer?

Nullmailer, on the other hand, is a lightweight MTA designed for use on systems where a full-featured MTA like Sendmail or Postfix is not necessary or desirable. Nullmailer is a “null” MTA in that it does not have the ability to receive messages or act as a full mail server. Instead, it is designed to simply forward outgoing messages to a more capable MTA, such as Gmail’s SMTP server or your hosting provider’s email server. This can be useful in situations where you do not have full control over the server you are using, or where you do not want to install and configure a full-featured MTA.

List of Popular Linux Nullmailers

The following page is a great resource

nullmailers

linuxmafia.com

Nullmailer – http://untroubled.org/nullmailer/
sSMTP – https://github.com/Raymonds84/ssmtp
esmtp – http://esmtp.sourceforge.net/
mSMTP – https://marlam.de/msmtp/
mini_sendmail – https://acme.com/software/mini_sendmail/
nbsmtp – https://nbsmtp.ferdyx.org/
smtp-cli – https://github.com/mludvig/smtp-cli
smtp-forwarder – https://github.com/agentzh/smtp-forwarder
sendEmail – http://caspian.dotconf.net/menu/Software/SendEmail/
sendEmail-SSL-wrapper – https://github.com/wildsau/sendEmail-ssl-wrapper

Summary of MTA vs Nullmailer

In summary, an MTA is responsible for sending and receiving email messages between servers, while Nullmailer is a lightweight MTA designed for forwarding outgoing messages to a more capable MTA.

Option 1 – Install an MTA (Mail Transport Agent)

You can install any of the popular MTA’s out there; I prefer Exim but Postfix or sendmail are perfectly fine. But are sometimes overkill.

Option 2 – Install a Nullmailer (ssmtp)

I’ve always enjoyed using ssmtp with Postmark, Sendgrid or Mailgun as a quick and easy setup for an MTA on a Linux server.

ssmtp is No Longer Maintained

Unfortunately, ssmtp is no longer maintained. Below is the original Github repository, from what I can tell, but it might be a mirror.

There is another Github repository that has patches for ssmtp.

Option 3 – msmtp an alternative to ssmtp

I was recommended msmtp by someone who read this article, I haven’t used it yet so I don’t have instructions right now.

msmtp – download

marlam.de

Changelog

04-04-2023 – Updated page to reflect MTA and nullmailer

Sending Email from your Server using an MTA or Null Mailer (Mail Transport Agent)

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