How to check from header in wp_mail wordpress

In WordPress, you can check the headers of an email sent using the wp_mail function by using the wp_mail_failed action hook.

Here's an example of how you can do it:

function check_email_headers($error, $msg, $header, $attachments) {
    // Check the headers
    if (isset($header['X-Mailer'])) {
        echo "X-Mailer: ". $header['X-Mailer']. "<br>";
    }
    if (isset($header['Content-Type'])) {
        echo "Content-Type: ". $header['Content-Type']. "<br>";
    }
    //... check other headers you're interested in
}
add_action('wp_mail_failed', 'check_email_headers', 10, 4);

In this example, the check_email_headers function is called whenever an email is sent using wp_mail. The function takes four arguments: $error, $msg, $header, and $attachments. The $header argument is an array of headers, where each key is the header name and each value is the header value.

You can access the headers using the $header array, like this:

if (isset($header['X-Mailer'])) {
    echo "X-Mailer: ". $header['X-Mailer']. "<br>";
}

This code checks if the X-Mailer header is set, and if so, it echoes the value of that header.

You can also use the wp_mail function's headers argument to set custom headers. For example:

$headers = array('X-Mailer' => 'WordPress');
wp_mail($to, $subject, $message, $headers);

This code sets the X-Mailer header to WordPress when sending the email.

Note that the wp_mail function returns true on success and false on failure. If the email fails to send, the wp_mail_failed action hook is triggered, and you can access the error message using the $error argument.