When you have presorted your data, you are no longer able to make modifications to the data or the selection of records and sort order.
If you want to display the data in the original order or make modifications to your data, you have to remove the postal sortation for your mailing. After making the changes, you can then re-sort the data using the presort settings you specified before.
To remove presort:
While the Datasheet is displayed, Click Remove Presort in the Postal Presort Group on the Postal tab.
FlexMail will remove the postal sortation. The data will be displayed in its original order, presort data fields will be removed from the Datasheet, and the additional views displaying the presort documents will be destroyed.