[event handler] onsent [event type] MessagingEvent [short description] handles sent messages [event name] 
sent
r e c e i v e d
s e n t
d e l i v e r y s u c c e s s
d e l i v e r y e r r o r
s e r v i c e a d d e d
s e r v i c e r e m o v e d