What steps can be taken to troubleshoot and resolve email delivery issues when using the mail() function in PHP?

Email delivery issues when using the mail() function in PHP can be caused by various factors such as incorrect email headers, server configuration issues, or being marked as spam by the recipient's email provider. To troubleshoot and resolve these issues, you can check the email headers, verify the recipient's email address, ensure proper server configuration, and avoid using spam-triggering words in the email content.

// Example code snippet to troubleshoot and resolve email delivery issues
$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";

if (mail($to, $subject, $message, $headers)) {
    echo "Email sent successfully!";
} else {
    echo "Failed to send email. Please check your server configuration and email content.";
}