Is it necessary to include the "http://" protocol in HTML links when sending emails with PHP, or can email clients automatically recognize and format links without it?

When sending emails with PHP, it is not necessary to include the "http://" protocol in HTML links. Email clients can automatically recognize and format links without it. This means you can simply include the domain and path in the href attribute of the anchor tag.

<?php
$to = "recipient@example.com";
$subject = "HTML Email with Link";
$message = "
<html>
<body>
<p>Click <a href='www.example.com'>here</a> to visit our website.</p>
</body>
</html>
";

$headers = "MIME-Version: 1.0" . "\r\n";
$headers .= "Content-type:text/html;charset=UTF-8" . "\r\n";

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