How can PHP developers ensure that emails sent from their scripts are not marked as spam by recipients' email servers?

To prevent emails sent from PHP scripts from being marked as spam, developers can ensure that the email headers are properly set with relevant information such as a valid sender address, a proper subject line, and a well-formatted email body. Additionally, using a reputable email service provider or setting up SPF, DKIM, and DMARC records can help improve email deliverability.

// Example PHP code snippet to send an email with proper headers

$to = "recipient@example.com";
$subject = "Test Email";
$message = "This is a test email.";

$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";

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