Garry - as regards the standard reports (ie not the Puppy School and Patient Sterilisation reports - which I suspect are user contributions from the resource library), I disagree that there is any benefit in simply adding an email address to the existing report.

If you want to mass email these customers then you need an export report, and the way to proceed would be to use the existing (1.8+) 'Export Email Addresses for Sales' report - either as a basis for what is needed (in the case of the new customer list) or to do what you want (I suspect that the Puppy School & Sterilisation cases both involve the sale of a specific product).

If you want to individually email them, then all you need is the customer id (shown on the reports) to access the customer, and click their email address to open the email write screen.

Regards, Tim G