How can PHP developers ensure that their test emails are being received and not marked as spam?

PHP developers can ensure that their test emails are being received and not marked as spam by setting up proper email headers, using a reputable email service provider, and avoiding common spam triggers like excessive use of links or attachments. Additionally, they can check their email deliverability by sending test emails to different email providers and checking the spam folders for any false positives.

// 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";

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