muzich/vendor/friendsofsymfony/user-bundle/FOS/UserBundle/Resources/config/mailer.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">

    <parameters>
        <parameter key="fos_user.resetting.email.template">FOSUserBundle:Resetting:email.txt.twig</parameter>
        <parameter key="fos_user.registration.confirmation.template">FOSUserBundle:Registration:email.txt.twig</parameter>
    </parameters>

    <services>
        <service id="fos_user.mailer.default" class="FOS\UserBundle\Mailer\Mailer" public="false">
            <argument type="service" id="mailer" />
            <argument type="service" id="router" />
            <argument type="service" id="templating" />
            <argument type="collection">
                <argument key="confirmation.template">%fos_user.registration.confirmation.template%</argument>
                <argument key="resetting.template">%fos_user.resetting.email.template%</argument>
                <argument key="from_email" type="collection">
                    <argument key="confirmation">%fos_user.registration.confirmation.from_email%</argument>
                    <argument key="resetting">%fos_user.resetting.email.from_email%</argument>
                </argument>
            </argument>
        </service>

        <service id="fos_user.mailer.twig_swift" class="FOS\UserBundle\Mailer\TwigSwiftMailer" public="false">
            <argument type="service" id="mailer" />
            <argument type="service" id="router" />
            <argument type="service" id="twig" />
            <argument type="collection">
                <argument key="template" type="collection">
                    <argument key="confirmation">%fos_user.registration.confirmation.template%</argument>
                    <argument key="resetting">%fos_user.resetting.email.template%</argument>
                </argument>
                <argument key="from_email" type="collection">
                    <argument key="confirmation">%fos_user.registration.confirmation.from_email%</argument>
                    <argument key="resetting">%fos_user.resetting.email.from_email%</argument>
                </argument>
            </argument>
        </service>

        <service id="fos_user.mailer.noop" class="FOS\UserBundle\Mailer\NoopMailer" public="false" />
    </services>

</container>