Closing out of the preview using the small red X in the upper left corner may close the preview without displaying the prompt.

When previewing standard receipts, and upon closing the preview screen with the X in the upper right corner, you receive the prompt 'would you like to mark gifts as receipted'. There is not a way to alter when this prompt appears as it is hard coded. Answer No to the prompt, then once you have them printed, re-process them through Mail and that time answer Yes.