I know it's not the email provider, but I needed an email provider that gets notifications on any browser. And it seems very rare.
Dude my "book" has 10 bytes in it
It's taking long not because it's processing anything but because it's done on purpose, maybe also the kindle doesn't connect to amazon all the time, but on all my tries, i never got faster than 1minute.
After some persistence, I finally might have found something though after looking to about 10 email providers I found this:
www.mailinator.com
You receive the email nearly instantly, there is no login, no password, this is heaven. Of course it seems like the inbox is public or something, but that's not a problem. I just hope I can keep using the same email though, not to have to change it every time.