How to Send Emails from PHP Securely and Efficiently

Sending emails from web applications is a crucial function for various purposes, such as user verification, notifications, and transactions. However, many developers still rely on PHP’s mail() function, which has significant limitations in terms of security, reliability, and compliance with modern email delivery standards.

In this article, we explore different strategies for sending emails from PHP securely, ensuring proper delivery and avoiding potential issues.

The Problem with Using PHP’s mail() Function

PHP includes the mail() function for sending emails without external libraries. While it appears to be a simple solution, it has several drawbacks:

• No SMTP authentication: Modern mail servers block unauthenticated messages.
• High rejection rates: Gmail, Outlook, and other providers may flag these emails as spam.
• Limited capabilities for attachments or custom headers.
• Lack of delivery tracking or monitoring features.

Basic Example Using mail()

<?php
$to = "user@example.com";
$subject = "Test Email";
$message = "This is a test email sent from PHP.";
$headers = "From: sender@domain.com";

mail($to, $subject, $message, $headers);
?>

While this function may be useful in testing environments, it is not recommended for production applications.

Recommended Alternatives for Sending Emails from PHP

To ensure emails are reliably delivered, it is best to use dedicated email libraries or transactional email services.

1. Using PHPMailer for SMTP Authentication

PHPMailer is one of the most popular libraries in PHP for sending emails with secure SMTP authentication.

Installing PHPMailer

composer require phpmailer/phpmailer

Sending Email Using PHPMailer and SMTP

<?php
use PHPMailer\PHPMailer\PHPMailer;
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 = 'user@example.com';
    $mail->Password = 'securepassword';
    $mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;
    $mail->Port = 587;

    $mail->setFrom('sender@example.com', 'Sender Name');
    $mail->addAddress('recipient@example.com');

    $mail->isHTML(true);
    $mail->Subject = 'Test Email with PHPMailer';
    $mail->Body    = '<b>This is a test email sent with PHPMailer.</b>';

    $mail->send();
    echo 'Email sent successfully';
} catch (Exception $e) {
    echo "Error: {$mail->ErrorInfo}";
}
?>

Advantages of Using PHPMailer

• Supports secure authentication (SMTP with TLS/SSL).
• Allows attachments and HTML formatting.
• Reduces the likelihood of emails being marked as spam.

2. Using a Transactional Email Service

Services like Mailgun, Acumbamail, SendGrid, or Amazon SES provide higher deliverability rates and advanced tracking features.

Example Using Mailgun API

<?php
$api_key = "your_api_key";
$domain = "sandboxXXXX.mailgun.org";
$to = "user@example.com";
$subject = "Email from Mailgun";
$message = "Hello, this is an email sent with Mailgun.";

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "https://api.mailgun.net/v3/$domain/messages");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, [
    'from' => 'Sender <sender@example.com>',
    'to' => $to,
    'subject' => $subject,
    'text' => $message
]);
curl_setopt($ch, CURLOPT_USERPWD, "api:$api_key");

$result = curl_exec($ch);
curl_close($ch);
echo $result;
?>

Advantages of Using Services Like Mailgun

• Higher deliverability rates with fewer spam issues.
• Provides analytics and delivery confirmation.
• Advanced security features with authentication, SPF, and DKIM.

How to Prevent Emails from Being Marked as Spam

To ensure successful email delivery, follow these best practices:

1. Configure SPF, DKIM, and DMARC

• SPF (Sender Policy Framework): Defines authorized mail servers for your domain.
• DKIM (DomainKeys Identified Mail): Adds a cryptographic signature to verify authenticity.
• DMARC (Domain-based Message Authentication, Reporting & Conformance): Establishes policies for handling suspicious emails.

Example SPF Record

v=spf1 include:_spf.mailgun.org ~all

Example DKIM Record

default._domainkey.yourdomain.com TXT "v=DKIM1; k=rsa; p=MIF..."

Example DMARC Record

_dmarc.yourdomain.com TXT "v=DMARC1; p=quarantine; rua=mailto:report@yourdomain.com"

2. Use Secure Connections with TLS/SSL

Always use encrypted connections when sending emails.

Example configuration in PHPMailer:

$mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;
$mail->Port = 587;

3. Avoid Spam Triggers

• Do not use words like “Exclusive offer,” “Free,” or “Click here.”
• Do not send bulk emails without user consent.
• Ensure the Reply-To address matches a verified domain.

Conclusion

Sending emails from PHP requires careful consideration. While the built-in mail() function may seem convenient, it is not suitable for production use. Using PHPMailer or a transactional email service such as Mailgun, Acumbamail or SendGrid ensures better deliverability and reduces the risk of emails being flagged as spam.

Proper configuration of SPF, DKIM, and DMARC records, along with secure SMTP authentication, will make your emails more reliable and compliant with modern security standards.

If your web application depends on email communication, implementing the best strategy is essential to ensure efficiency and security.