What are common issues when using the mail() function in PHP?

One common issue when using the mail() function in PHP is that emails may be marked as spam by the recipient's email provider. To solve this issue, you can set proper headers such as "From", "Reply-To", and "MIME-Version" to ensure the email is recognized as legitimate. Additionally, you can use a third-party email service like SendGrid or Mailgun to improve deliverability.

$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=utf-8\r\n";

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