I would really like to see you change phrasing under "Do i have to use Big Mail Online?" To state that to have any notifications at all it requires it, and not how you currently present it.
To be forced to sign up on yet another account online, just to get notifications is a no go for me. And i imagine i will not be alone. Too bad, you had soo much going for you.
How is fetch confusing to explain? A user that chooses fetch is in most cases already aware of fetch limit/behaviour