What potential issues can arise when sending emails with PHP Mail function?

One potential issue that can arise when sending emails with the PHP Mail function is that the emails may be marked as spam by the recipient's email server. This can happen if the email headers are not properly set or if the email content triggers spam filters. To solve this issue, you can set appropriate headers, such as a From address and a MIME version, and ensure that the email content is not overly promotional or contains suspicious links.

$to = "recipient@example.com";
$subject = "Test Email";
$message = "This is a test email.";
$headers = "From: sender@example.com\r\n";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "Content-type: text/plain; charset=iso-8859-1\r\n";

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