Minecraft Email from Username

I was interested in making a cracker that works for both people wanting to use the Minecraft client but also for people wanting to use their Mojang account, but in order to do this, I would need some way of finding out their emails. If there is a way, please tell me, if not, oh well.

Go to https://account.mojang.com/migrate and log in with the alt, it will then ask you if you want to use the current email or use a different email, by asking this it will reveal the email bound to it.

Good luck.

I suppose that would work, but what I really was wondering was if there was a way to do it without passwords.