1. Go to Analysis > Information Library 
  2. Click to Add a new Ad-hoc query 
  3. Select the source view of Constituents and click OK. 
  4. In the middle column, drag "Is inactive" to include Records Where. Set this to be equal to "No."
  5. In the middle column, also drag "Type" to Include Records Where and change the operator to be "One of" or "Equal to"the constituent types you are looking for. We recommend starting with Individuals and Organizations.  
  6. From the left column, highlight Email Addresses. From the middle column, drag "Email Address" into Include Records Where. Set this to be not blank. 
  7. From the middle column, also drag "Email Address" to Results Fields to Display.
  8. Remove "Name" from Results Fields to Display.
  9. Next highlight Constituents at the very top in the left column. From the middle column, drag "Lookup ID" from the middle column to Results Fields to Display. Click the Sigma sign and select to COUNT(Lookup ID). This will allow us to count all of the unique Lookup IDs for each email address in our results. 
  10. To only see constituents that have a count greater than 1 (and therefore a possible duplicate record), go to the Set Sort and Group Options Tab. drag "COUNT(Lookup ID) to Include Records Where and set this filter to be "Greater than or equal to" 2. This will show you only those email addresses that have more than 2 Lookup IDs associated with it. 
  11. On the Set Save Options Tab, save your query.