Send email from Linux: a guide

Linux operating system powers a huge portion of the world’s servers and supercomputers! 

In fact, ~96% of web servers (out of the top 1M) and the 500 fastest supercomputers worldwide use Linux. Fun trivia – SpaceX used Linux-based systems to successfully complete 65 space missions. 

Does Linux send email?

Oh yes, system administrators can easily send emails with the Linux command line using various tools available in the ecosystem. In this article, we’ll walk you through the steps to send emails with Linux using some popular command-line tools.

Send Emails in Linux with Command Line

The following sections list the most popular commands, you’ll learn how to send with Mailtrap Sending API, and we included a section to test emails in a sandbox with Mailtrap Testing. 

Note that some of the typical command options you can use to send emails with a Linux command line interface  include:

• -a – to denote an attachment
• -b – (BCC) the blind copy
• -c – (CC) the email address copy
• -s – to denote email subject

We included the installation steps on Debian and RedHat-based distributions for the commands that might not be on Linux by default. Note that some may require installing an additional package manager. But if you already have them installed, feel free to skip these steps. 

The curl command

The curl command is a versatile tool for transferring data between servers and applications. It can also be used to send emails from the command line in Linux. 

Here’s how to use it:

First, create a plain text file containing the email message you want to send. You can use a text editor like nano or vim to create the file. For example, let’s create a file called message.txt with the following content:

From: "User Name" <username@example.com>
To: "John Doe" <john@example.com>
Subject: You are awesome

Congrats for sending a test email with Mailtrap on Linux.

Replace the credentials, and modify the subject and body of the email as needed.

Next, use the curl command to send the email. Here’s the basic syntax:

curl \
--ssl-reqd \
--url 'https://send.api.mailtrap.io/api/send:587' \
--user 'YourMailtrapPassword or API token' \
--mail-from from@example.com \
--mail-rcpt to@example.com \
--upload-file - message.txt
From: “User Name” <username@example.com>
To: “John Doe” <john@example.com>
Subject: You are awesome!
Content-Type: multipart/alternative; boundary="boundary-string"

--boundary-string
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

Congrats for sending test email with Mailtrap on Linux!

--boundary-string
Content-Type: text/html; charset="utf-8"
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
--boundary-string--

The mail command

Aptly named, the mail command does exactly that – sends emails from the command line. It’s a good option to programmatically generate emails from web apps or Shell scripts, particularly in systems sans a GUI. 

Step 1: Install mail

If you’re running a Debian-based distribution like Ubuntu, use the following commands to update and install it:

$ sudo apt-get update

Then, run the following command to install mailutils:

$ sudo apt install -y mailutils

If you’re running a Red Hat-based distribution like CentOS, you can use the following command:

sudo yum install mailx

Note: When installing mailutils on Debian-based distributions, the action automatically installs Postfix. Follow the Postfix Configuration wizard to connect it to your website. 

Step 2: Postfix Configuration

Continue configuring Postfix so it works with your email provider. To do that, first, navigate to the configuration file below and edit it. 

$ sudo nano /etc/postfix/main.cf

At the end of the file, you’ll find relayhost =. Delete the line and add the following in its place: 

relayhost = [live.smtp.mailtrap.io]:587
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
smtp_tls_CAfile = /etc/postfix/cacert.pem
smtp_use_tls = yes

Save the file, then exit. 

Step 3: DB Files and Password

To keep your credentials safe, create a file using the snippet below: 

$ sudo nano /etc/postfix/sasl_passwd

Then, populate the file with your credentials.

[live.smtp.mailtrap.io]:587 username@example.com:password

If you aren’t a Mailtrap user, list your credentials, then save and exit. 

Next, use the postmap command to make a hash database. 

$ sudo postmap /etc/postfix/sasl_passwd

Now, navigate to the <strong>/etc/postfix/</strong>directory, and you should be able to find the <strong>sasl_passwd.db</strong>file. 

Step 4: Certification

Use the snippet below to change the certs directory. 

$ cd /etc/ssl/certs

Get the Thwate cert. 

$ sudo wget https://www.thawte.com/roots/thawte_Primary_Root_CA.pem

Create certificate.

$ cat /etc/ssl/certs/thawte_Primary_Root_CA.pem | sudo tee -a /etc/postfix/cacert.pem

Inspect the configuration by locating the cacert.perm under /etc/postfix directory.

Step 5: Send an email

Now that mail is installed and configured, you can send an email using the following command:

echo "This email body is sent with Mailtrap" | mail -s "Mailtrap Linux email" recipient@example.com

You can change the body and the subject in the echo command, and the recipient, of course.

Click here to Maitrap blog post about how to launch mpack and mutt commands.