use null://null for MAILER_DSN by default

symfony/mailer/4.3/manifest.json

@@ -3,7 +3,7 @@
         "config/": "%CONFIG_DIR%/"
     },
     "env": {
-        "#1": "MAILER_DSN=smtp://localhost"
+        "#1": "MAILER_DSN=null://null"
     },
     "docker-compose": {
         "docker-compose.override.yml": {

symfony/mailer/5.4/config/packages/mailer.yaml

@@ -1,8 +0,0 @@
-framework:
-    mailer:
-        dsn: '%env(MAILER_DSN)%'
-
-when@test:
-    framework:
-        mailer:
-            dsn: null://null

symfony/mailer/5.4/manifest.json

@@ -1,18 +0,0 @@
-{
-    "copy-from-recipe": {
-        "config/": "%CONFIG_DIR%/"
-    },
-    "env": {
-        "#1": "MAILER_DSN=smtp://localhost"
-    },
-    "docker-compose": {
-        "docker-compose.override.yml": {
-            "services": [
-                "mailer:",
-                "  image: schickling/mailcatcher",
-                "  ports: [1025, 1080]"
-            ]
-        }
-    },
-    "aliases": ["mailer", "mail"]
-}

symfony/mailer/5.4/post-install.txt

@@ -1,14 +0,0 @@
-  * You're ready to send emails.
-
-  * If you want to send emails via a supported email provider, install
-    the corresponding bridge.
-    For instance, <info>composer require mailgun-mailer</> for Mailgun.
-
-  * If you want to send emails asynchronously:
-
-    1. Install the messenger component by running <info>composer require messenger</>;
-    2. Add <info>'Symfony\Component\Mailer\Messenger\SendEmailMessage': amqp</> to the
-       <info>config/packages/messenger.yaml</> file under <info>framework.messenger.routing</>
-       and replace <info>amqp</> with your transport name of choice.
-
-  * <fg=blue>Read</> the documentation at <comment>https://symfony.com/doc/master/mailer.html</>