From

 

The columns in this group box are only available if the Document Type is EMAIL.

 

To add an EMAIL_FROM column to the Datawindow, you MUST add that column from the SQL Painter for that query utilizing the Compute tab. You cannot add a simple computed field named EMAIL_FROM to the data window painter. It must originate from the SQL.

This column serves as the default From e-mail address for all e-mail messages merged for this document if the Datawindow does not contain a column named EMAIL_FROM. If an EMAIL_FROM column exists in the Datawindow, the value pulled from that query will be used as the From e-mail address.