Are there specific headers that should be included when sending HTML emails to avoid being marked as spam by email providers?

To avoid HTML emails being marked as spam by email providers, it is important to include specific headers in the email. Some key headers to include are the "From" header with a valid email address, the "Reply-To" header, the "Content-Type" header specifying the email format as text/html, and the "MIME-Version" header. 

<?php
$to = "recipient@example.com";
$subject = "Your Subject Here";
$message = "<html><body>Your HTML content here</body></html>";
$headers = "From: sender@example.com\r\n";
$headers .= "Reply-To: sender@example.com\r\n";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "Content-Type: text/html; charset=ISO-8859-1\r\n";

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

Keywords

PHP HTML emails headers spam email providers

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