I had a list of about 300 people when I launched preorders and about 30% of them converted to paying customers. I was sending out weekly updates with progress toward preorders, and then after preorders started I sent out weekly updates with download links for people who paid and "buy now for X% off, won't last long" messages for people who hadn't.

The whole story is here: https://www.petekeen.net/adventures-in-self-publishing