Update mailer.rst

Author: alexander-schranz

mailer.rst

@@ -1024,12 +1024,10 @@ the transport to be handled later (see :ref:`messenger-worker`).
 Events
 ------
 
-The mailer component also throws a events:
-
 MessageEvent
 ~~~~~~~~~~~~
 
-The MessageEvent allows you to manipulate the send message:
+The MessageEvent allows the transformation of a Message and the Envelope before the email is sent:
 
 .. code-block:: php