On the diary you are able to send emails to clients from their appointments. To do this click on the appointment you wish to send an email to. This will bring up the below Appointment Details screen.
Highlighted in this image at the bottom left hand corner is Communication. Select this and you will be given a number of options of different communications you can send to the selected appointment. At the top of this list you will have the option to send an Appointment Reminder email to the patient.
Further down the list is the option for Email and when this is selected it will bring up all the email templates that have been created for a patient. You can select one of these and this will bring you to the email template that has been populated with all the appointment details. You can add more information in here to the email but won't be saved to the template.
To send just click the Send button on the bottom right hand corner.