What potential issues can arise when using the mail() function in PHP for sending emails from a contact form?

One potential issue when using the mail() function in PHP for sending emails from a contact form is that the emails may be marked as spam by the recipient's email provider. To solve this issue, you can set additional headers in the mail() function to specify the sender's email address and improve the email's deliverability.

$to = "recipient@example.com";
$subject = "Subject of the email";
$message = "This is the message body of the 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);