How can PHP headers affect the deliverability of emails, especially to providers like AOL?

PHP headers can affect email deliverability, especially to providers like AOL, by influencing how the email is perceived by spam filters. To improve deliverability, set appropriate headers such as "From," "Reply-To," and "Return-Path" to valid email addresses associated with your domain. Additionally, ensure that the email content is relevant and not flagged as spam by including proper DKIM and SPF records.

// Set email headers
$to = "recipient@example.com";
$subject = "Subject";
$message = "Email content";
$headers = "From: sender@example.com\r\n";
$headers .= "Reply-To: sender@example.com\r\n";
$headers .= "Return-Path: sender@example.com\r\n";

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