ID732 will email a Thank You letter directly to your customers. It looks at the active contact with an email that is linked to the Sales Order. It will also look at the Sales Order type (typically Equipment) that you specify above in variable W. ID89 will email the PDF Thank You letter to you/person listed in subscription, to review/forward/print and mail.
Use the alert variables to enable contacts to send to (or not), as well as making sure your contacts don't get flooded with emails, but indicating the # of days between emails.
Your contact will receive a letter that you compose, see sample below for types of content you may want to include.
VarW = SalesOrder Type (Equipment
VarX = CustomPropertyAttribute on Customers to be EXCLUDED
VarY = CustomPropertyAttribute on Contacts to be EXCLUDED
VarZ = Days between e-mails to any given customer (not contact), so as to not flood the customer if they buy multiple machines