update service section

docs/ecolyo/application/services.md

@@ -37,3 +37,10 @@ Main steps are the following:
  - Fetches metadata to customize the mail (Public name, instance url).
  - Build the mail.
  - Send the mail.
+
+### Sending mail
+
+Doc of cozy for sendmail worker: https://docs.cozy.io/en/cozy-stack/workers/#sendmail-worker
+
+!!! Send mail in local
+    In local you can use the mail hog tools to see the mail sent by the stack using http://cozy.tools:8025/
\ No newline at end of file