I hope they quickly sent a thank-you letter to everyone who gave a donation, no matter how much or how little! On a strictly business basis, that’s the right thing to do. The person who gives you a $25 donation may be waiting to see what you do with it before becoming a major donor. The person who gives a a little every year may be thinking about what organization to benefit in their will. Show them that they matter to you, or you may miss your chance. And besides, it’s the right thing to do!