<!-- app/config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        http://symfony.com/schema/dic/services/services-1.0.xsd">

    <services>
        <service id="app.mailer">
        <!-- ... -->
        </service>

        <service id="app.newsletter_manager" class="AppBundle\Newsletter\NewsletterManager">
            <argument type="service" id="app.mailer"/>
        </service>
    </services>
</container>