Smart filter that find people who got a mail exactly 3 days ago

Hi,

im trying to make a smart filter that finds all who Marketo have send a mail to 3 days again exactly, and it needs to be dynamic, so i changes each day.

I tried to use

Was send Mail: in past 3 days.    This it seems 'in past 3 days' includes all of the past 3 days, so not exactly 3 days, but '1 or 2 or 3' days ago?

How can i make this Smart filter?