How to install PHPMailer manually in Plesk for Linux?

Question

How to install PHPMailer manually in Plesk for Linux?

Answer

1. Connect to the server via SSH

2. Download PHPMailer and unzip the archive:

   # wget https://github.com/PHPMailer/PHPMailer/archive/master.zip
   # unzip master.zip

3. Move PHPMailer to the necessary location, for example:

   # mv PHPMailer-master/ /var/www/vhosts/example.com/

4. Add this location to include_path in Domains > example.com > PHP Settings:

   Note: do not remove existing path; to separate directories, add a colon (:) between them, for example:
   .:/usr/share/php:/usr/share/pear:/var/www/vhosts/example.com/

5. Modify the existing PHP script used for sending mail, for example:

   <?php
   // Import PHPMailer classes into the global namespace
   // These must be at the top of your script, not inside a function
   use PHPMailer\PHPMailer\PHPMailer;
   use PHPMailer\PHPMailer\Exception;
   //Load Composer's autoloader
   require 'vendor/autoload.php';
   $mail = new PHPMailer(true); // Passing true enables exceptions
   try {
   //Server settings
   $mail->SMTPDebug = 2; // Enable verbose debug output
   $mail->isSMTP(); // Set mailer to use SMTP
   $mail->Host = 'smtp1.example.com;smtp2.example.com'; // Specify main and backup SMTP servers
   $mail->SMTPAuth = true; // Enable SMTP authentication
   $mail->Username = 'user@example.com'; // SMTP username
   $mail->Password = 'secret'; // SMTP password
   $mail->SMTPSecure = 'tls'; // Enable TLS encryption, ssl also accepted
   $mail->Port = 587; // TCP port to connect to
   //Recipients
   $mail->setFrom('from@example.com', 'Mailer');
   $mail->addAddress('joe@example.net', 'Joe User'); // Add a recipient
   $mail->addAddress('ellen@example.com'); // Name is optional
   $mail->addReplyTo('info@example.com', 'Information');
   $mail->addCC('cc@example.com');
   $mail->addBCC('bcc@example.com');
   //Attachments
   $mail->addAttachment('/var/tmp/file.tar.gz'); // Add attachments
   $mail->addAttachment('/tmp/image.jpg', 'new.jpg'); // Optional name
   //Content
   $mail->isHTML(true); // Set email format to HTML
   $mail->Subject = 'Here is the subject';
   $mail->Body = 'This is the HTML message body <b>in bold!</b>';
   $mail->AltBody = 'This is the body in plain text for non-HTML mail clients';
   $mail->send();
   echo 'Message has been sent';
   } catch (Exception $e) {
   echo 'Message could not be sent. Mailer Error: ', $mail->ErrorInfo;
   }

Additional information

https://github.com/PHPMailer/PHPMailer