Install Mailgun for my Ionic/Laravel App

I have an app build with Ionic/Angular and with a Laravel backend. For the e-mail function I need Mailgun to be installed. I need somebody with is familiar with Laravel and CentOS, because some changes need to be made. I tried to install Mailgun but I get an error for Guzzle QUOTE Class 'GuzzleHttp\Client' not found UNUQOTE I tried to run composer but I suppose that something with Ioncube is wrong. Maybe it need to be updated too. So please bit only if you have the knowhow to handle with these languages.