I got this idea from Kent State, on sending a "Giftiversary card." We have them for donors who have given, but not in the last one, two, or three years. Because we are a smaller office, we left it as generic as possible so I could handwrite names and personalized messages. We have also included remittance cards and envelopes should they want to include payment, and will be using regular postage stamps, not running it through as non-profit stamps.