Symfony 3 - MailGun set up

1. Install bundle https://github.com/tehplague/swiftmailer-mailgun-bundle
2. Follow instructions to this bundle
cspoo_swiftmailer_mailgun:
    key: "key-xxxxxxxxxx"
    domain: "mydomain.com"
    http_client: 'httplug.client'(This is required field) 

# Swiftmailer Configuration
swiftmailer:
    transport: "mailgun"
    #spool:     { type: memory } # This will start sending emails on kernel.terminate event
    
To make this config param allowed :  http_client: 'httplug.client'(This is required field) 
1.composer require php-http/guzzle6-adapter
2.composer require php-http/httplug-bundle
3.
public function registerBundles()
{
    $bundles = array(
        // ...
        new Http\HttplugBundle\HttplugBundle(),
    );
}
4. You need to register on mailgun service. You will receive temp mail domain.
To send email to some email you should add it as authorized recipients in the settings of this domain