Hi,
1. You can set up the workflow for Maintenance Notification through configuration by setting up the work flow .
This is a standard workflow so only customizing is required .
SPRO->Plant Maintenance and Customer Service-> Maintenance and Service Processing-> Notification Processing-> Set workflow for Maintenance Notification .
2. You can write the code at the in the implementation of BADI NOTIF_EVENT_POST -> method CHECK_DATA_AT_POST if you have to send a mail to the custom list of recipients .
Anjan