What are the key considerations when using PHP to interact with external mail servers for sending emails?

When using PHP to interact with external mail servers for sending emails, it is important to consider security measures such as validating user input to prevent injection attacks, using secure connections (such as SMTP over SSL), and properly sanitizing and validating email content to prevent spam or malicious code injection. 

// Example PHP code snippet for sending an email using PHPMailer with secure SMTP connection

use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\SMTP;
use PHPMailer\PHPMailer\Exception;

require 'vendor/autoload.php';

$mail = new PHPMailer(true);

try {
    $mail->isSMTP();
    $mail->Host = 'smtp.example.com';
    $mail->SMTPAuth = true;
    $mail->Username = 'your_email@example.com';
    $mail->Password = 'your_password';
    $mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;
    $mail->Port = 587;

    $mail->setFrom('your_email@example.com', 'Your Name');
    $mail->addAddress('recipient@example.com', 'Recipient Name');

    $mail->isHTML(true);
    $mail->Subject = 'Subject';
    $mail->Body = 'Email body content';

    $mail->send();
    echo 'Email sent successfully';
} catch (Exception $e) {
    echo "Message could not be sent. Mailer Error: {$mail->ErrorInfo}";
}

Keywords

SMTP PHPMailer authentication TLS error handling

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