Each donor will receive a confirmation email after making a successful donation. Included in that email is a customizable thank-you message to the donor. This is a great place to let your donors know they're appreciated, how their donation will be used, and any other important information you want to share.
A default message is included with each campaign. To edit this, simply go to Donations in the campaign setup menu. Scroll down and you will see the the box to customize the thank you email for donor receipts.
Other articles you may find helpful: