For some reason if you amend Manager > Settings > Point of sale > Receipts > Custom Receipt Text, it only adds it to printed receipts, not email ones, which is unfathomably ridiculous!.

We have many instances where clients want an email, as they can claim treatments from employers or schemes, and they need an email as proof. This email also has to say the qualification of their therapist. Which is what I want to add to every email receipt sent