Can I send a postcard asking for a review to the customer’s address?
I think it is more personal it’s better than an email.
Officially, Amazon frowns on any added “review request” efforts outside of the emails they send on your behalf. Adding a generic “leave a review” on packaging or order inserts (if handling your own fulfillment) is really the best way to handle this without running afoul of Amazon — plus postcard mailings aren’t cheap! I’m not sure that it would be worth the money. Hope this helps, good luck.