Beef up the example inventory

Signed-off-by: martin f. krafft <madduck@madduck.net>
diff --git a/examples/classes/mail/server.yml b/examples/classes/mail/server.yml
new file mode 100644
index 0000000..5e0064d
--- /dev/null
+++ b/examples/classes/mail/server.yml
@@ -0,0 +1,5 @@
+classes:
+  - mail
+parameters:
+  mail:
+    role: server