Setup Server for Sending Email using sSMTP

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LHammonds
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Setup Server for Sending Email using sSMTP

Post: # 696Post LHammonds »

Email Overview

Many PHP web applications utilize PHP's built-in "mail" function which means we need to configure php.ini to use a mail client that will send email. System scripts like fail2ban can also make use of command-line email.

It seems like an industry standard to use "sendmail" based on all the tutorials out there but sendmail is a mail server itself which can receive mail which is overkill for our purposes. We only want to send outbound to a dedicated mail server...not turn each web server into a mail server.

For this reason, we will install a lightweight mail client called ssmtp that will allow sending outbound-only mail messages.

We will then modify PHP to utilize this mail client. The final step would be to configure the web application to send mail.

Mail Server Information
There are many scenarios surrounding how one might have a mail service.

For this tutorial, let's assume you have a mail server that you configured to act as a relay server for this specific server...which means you can send email to that server to be delivered locally or routed to another mail server if the destination is not local. Let's assume this relay server will not require login credentials but does require the FROM address to be specific. Let's also assume it does not require encryption.

Here are the settings used for this example: (be sure to change them throughout this article to match your environment)

Mail Relay Server Address: 192.168.107.25
Mail Relay Server Port: 25
Use TLS? No
From Address: webmaster@mydomain.com
To Address: YourEmailAddr@mydomain.com

Install and Configure SSMTP

Install the mail client:

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sudo apt -y install ssmtp
Backup the original configuration files:

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sudo cp /etc/ssmtp/ssmtp.conf /etc/ssmtp/ssmtp.bak
sudo cp /etc/ssmtp/revaliases /etc/ssmtp/revaliases.bak
Edit the main configuration file:

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sudo vi /etc/ssmtp/ssmtp.conf
Set the following (make sure to use your settings):

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root=
mailhub=192.168.107.25:25
hostname=localhost
FromLineOverride=YES
UseSTARTTLS=NO
#AuthUser=user@mydomain.com
#AuthPass=userpassword
NOTE: Some mail servers do not allow overriding the from address such as Gmail.

Edit the reverse alias file:

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sudo vi /etc/ssmtp/revaliases
Add the alias for "root" to be that of your desired "FROM" address. (make sure to use your settings)

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root:webmaster@mydomain.com
Modify PHP.ini for Apache

Edit the Apache PHP.ini

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sudo vi /etc/php/7.2/apache2/php.ini
Set the sendmail_path variable to point to the default sendmail path (which is a link to ssmtp)

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sendmail_path = /usr/sbin/sendmail -t
Or set the sendmail_path variable to point to ssmtp directly:

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sendmail_path = /usr/sbin/ssmtp -t
Modify PHP.ini for Command-Line

While we are making the mail command work for PHP inside Apache, we might as well do the same for the command-line interface.

Make the same changes above to this file as well.

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sudo vi /etc/php/7.2/cli/php.ini
Make the same changes here that you did above for Apache's PHP.ini

Send PHP Test Email

Create 2 PHP test scripts to send an email message from a web browser and the command line.

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sudo touch /var/www/html/testmail-web.php
sudo touch /var/www/html/testmail-cli.php
sudo chown www-data:root /var/www/html/testmail-*.php
sudo chmod 644 /var/www/html/testmail-*.php
Here is the code to add into the web test: (be sure to change the TO and FROM addresses to reflect your environment)

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sudo vi /var/www/html/testmail-web.php

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<html>
<head>
<title>Test mail</title>
</head>
<body>
<?php
ini_set( 'display_errors', 1 );
error_reporting( E_ALL );
$from = "webmaster@mydomain.com";
$to = "YourEmailAddr@mydomain.com";
$subject = "PHP Mail Test script - Web";
$message = "This is a test to check the PHP Mail functionality from a web browser";
$headers = "From:" . $from;
mail($to,$subject,$message, $headers);
echo "<p>Test email sent</p>";
?>
</body>
</html>
Here is the code to add into the command-line interface (cli) test: (be sure to change the TO and FROM addresses to reflect your environment)

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sudo vi /var/www/html/testmail-cli.php

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<?php
ini_set( 'display_errors', 1 );
error_reporting( E_ALL );
$from = "webmaster@mydomain.com";
$to = "YourEmailAddr@mydomain.com";
$subject = "PHP Mail Test script - cli";
$message = "This is a test to check the PHP Mail functionality from command line";
$headers = "From:" . $from;
mail($to,$subject,$message, $headers);
echo "Test email sent";
?>
Test from the command-line:

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php /var/www/html/testmail-cli.php
Now test from a browser:

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http://mydomain.com/testmail-web.php
If you have any issues, check /var/log/syslog for messages related to sSMTP

Remove the temporary PHP test scripts:

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sudo rm /var/www/html/testmail-*.php
Send Command-Line Test Email

Modify the recipient email address below and run the commands on the console and see if you received the test email:

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echo "To: recipient@mydomain.com" > /tmp/mail.txt
echo "Subject: Testing 1-2-3" >> /tmp/mail.txt
echo " " >> /tmp/mail.txt
echo "This is a test, this is only a test. If this had been a real emergency, I would not be sending this email" >> /tmp/mail.txt
/usr/sbin/ssmtp -t < /tmp/mail.txt
rm /tmp/mail.txt
Send Command-Line Test Email with HTML Format

Modify the recipient email address below and run the commands on the console and see if you received the test email:

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echo "To: recipient@mydomain.com" > /tmp/mail.txt
echo "From: AlternateName<device@mydomain.com" >> /tmp/mail.txt
echo "Subject: Testing 1-2-3 in HTML" >> /tmp/mail.txt
echo "Mime-Version: 1.0" >> /tmp/mail.txt
echo "Content-type: text/html; charset="“iso-8859-1”"" >> /tmp/mail.txt
echo " " >> /tmp/mail.txt
echo "<h1>This is a test, this is only a test.</h1><h2>If this had been a real emergency, I would not be sending this email</h2>" >> /tmp/mail.txt
echo "<img src='https://www.w3.org/WAI/tutorials/img/w3c-796023c4.png' />" >> /tmp/mail.txt
/usr/sbin/ssmtp -t < /tmp/mail.txt
rm /tmp/mail.txt

Web Application Email Settings

Enable email support however it is done in your application.
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