What are the potential reasons for emails not being delivered even though the mail() function in PHP returns TRUE?

The potential reasons for emails not being delivered even though the mail() function in PHP returns TRUE could be due to issues with the mail server configuration, spam filters blocking the email, incorrect recipient email address, or the email being marked as spam by the recipient's email provider. To solve this issue, you can try checking the mail server logs for any errors, ensuring the recipient email address is correct, and adjusting the email content to avoid being marked as spam.

// Example PHP code snippet to check for errors when sending an email
if (mail($to, $subject, $message, $headers)) {
    echo "Email sent successfully!";
} else {
    echo "Failed to send email. Check server logs for errors.";
}