Beef up the example inventory

Signed-off-by: martin f. krafft <madduck@madduck.net>
diff --git a/examples/classes/mail/relay.yml b/examples/classes/mail/relay.yml
new file mode 100644
index 0000000..28d3b26
--- /dev/null
+++ b/examples/classes/mail/relay.yml
@@ -0,0 +1,6 @@
+classes:
+  - mail
+parameters:
+  mail:
+    role: relay
+    port: 587