1. Click Management
  2. Click Mass Update
  3. Click Update Existing Accounts
  4. Select the Category and Query name from the drop down menus
  5. Mark Assign below the Update Type heading
  6. Below the Account Values heading, click the Mailing Status UDF
  7. Select Do Not Mail
  8. Click Next
  9. Preview the list of accounts that will be updated
  10. Click Next to run the Mass Update