You can send the email notification in Schedule from the appointment or service call window by choosing the Notify Customer  icon or by right-clicking the appointment or service call and then choosing Notify Customer.

Standard notifications

Appointment cancelled
Appointment created and scheduled
Appointment reassigned
Appointment rescheduled
Technician arrived
Technician checked out
Service call created
Service call created by ESMS email

Advanced communication HTML notifications

Technician arrived
Technician in Route (Dispatched)
Appointment Completed