1. Go to Analysis > Information Library.  Click Add an ad-hoc query.  Select the source view of Constituents and click Ok.
  2. On the left, click Appeal Mailing. 
  3. In the middle, if you want to filter on an entire mailing, click on Mailing and move that to Include Records Where and enter the exact name of your mailing.  If you want to look at one letter within a mailing, click on Letter in the middle and move that to Include Records Where and enter the exact name of your letter.  Note: if your letter name is not unique and has been used in other mailings, you will need to enter criteria of mailing name is equal to x and letter name is equal to x to ensure you are getting the right letter within the correct mailing.
  4. Go to the Set Save Options tab.  Enter a name for the query and click Save.  Process the results.