Auto-Communications are generated when some system procedures are recorded against a horse:
In the Main Screen click on Create Procedure
Select Horse
Select the Horse name from the dropdown
Select the System Procedure (ie Arrival)
Click on Next
Add the required fields (Agistment Details, Property)
Click on Add Procedure
Go to Communications
Go to the horse, click on the gearwheel
Select Recipients
Ensure that the email addresses are correct, then press Email all Recipients