How to set X-Mailgun-Campaign-Id header in Mailgun php API?

Question

How to set up header "X-Mailgun-Campaign-Id" in Mailgun php API?

I'm using the following code, but I don't know how to pass campaign ID in the header:

Mail::send('email.message', $data, function ($message) use ($data) {
    $message->to($data['to_email'], $data['to_name'])
        ->subject($data['subject'])
        ->from($data['from_email'], $data['from_name'])
        ->header('X-Mailgun-Campaign-Id', 'test campaign');
});

Answer 1

Solution has been found:

Mail::send('emails.test3', array(), function ($message) {
    $message->to('[email protected]')
        ->subject('Смоторим ответа об открытии')
        ->from('[email protected]');

    $headers = $message->getHeaders();
    $headers->addTextHeader('X-Mailgun-Variables', '{"id_message": "666"}');
    $headers->addTextHeader('X-Mailgun-Tag', 'test-tag');
    $headers->addTextHeader('X-Mailgun-Campaign-Id', 'sDas7d');
});

List of available headers are for the link https://documentation.mailgun.com/user_manual.html#sending-via-smtp