I'd like to know why it works. Does "10x superior onboarding emails" mean 10x better retention/conversion numbers? Backstory: I've been trying to improve retention in a complex system with ~10^5 users, and email doesn't seem to add too much gain. Focusing effort on the website seems to have a larger effect.

How are your emails 10x better? Is it the schedule (Day 1 ... day 4 ...day 7) of emails? The content ("Become a power user like Zach...")?

Unless you say why it is better, it is hard to see if that it is a no-brainer.