sSMTP is a lightweight SMTP client that allows you to send emails from the command line or from scripts on a Linux system. It is particularly useful for sending automated emails from servers or for testing email functionality in development environments. Unlike a full-fledged mail transfer agent (MTA) like Postfix or Sendmail, sSMTP is simpler and easier to configure, making it ideal for straightforward email-sending tasks.

In this article, we will cover how to install, configure, and use sSMTP on a Linux system. We will also provide practical examples to demonstrate its usage.

Examples:

1. Installation: To install sSMTP on a Debian-based system (like Ubuntu), use the following command:

   sudo apt-get update
   sudo apt-get install ssmtp

   For Red Hat-based systems (like CentOS), use:

   sudo yum install ssmtp

2. Configuration: The main configuration file for sSMTP is /etc/ssmtp/ssmtp.conf. Open this file in a text editor with root privileges:

   sudo nano /etc/ssmtp/ssmtp.conf

   Add the following configuration parameters, replacing the placeholders with your actual email server details:

   root=your_email@example.com
   mailhub=smtp.example.com:587
   AuthUser=your_email@example.com
   AuthPass=your_password
   UseSTARTTLS=YES
   UseTLS=YES

   Save and close the file.

3. Sending an Email: You can send an email using the ssmtp command. Here is an example of how to send an email from the command line:

   echo -e "Subject: Test Email\n\nThis is a test email." | ssmtp recipient@example.com

   For more complex emails, you can create a text file with the email content:

   To: recipient@example.com
   From: your_email@example.com
   Subject: Test Email
   
   This is a test email with more content.

   Save this file as email.txt and send it using:

   ssmtp recipient@example.com < email.txt

4. Automating Email Sending in Scripts: You can integrate sSMTP into your scripts to send automated emails. Here is a simple Bash script example:

   #!/bin/bash
   
   SUBJECT="Automated Email"
   TO="recipient@example.com"
   FROM="your_email@example.com"
   MESSAGE="This is an automated email sent from a script."
   
   echo -e "To: $TO\nFrom: $FROM\nSubject: $SUBJECT\n\n$MESSAGE" | ssmtp $TO

   Save the script as send_email.sh, make it executable, and run it:

   chmod +x send_email.sh
   ./send_email.sh