How do you change the columns in MRIS?

[John S.]

I'm sending sales comps to my clients and when they open the message, they see on the left hand side: sent date (see yellow highlight in picture below). 

I want them to see the sold date, not the sent date because the sent date is always the same for 1 message. It's not that useful. By having sold date, the buyer will have a better time analyzing comps. Do you know how to change this column to sold date?