PROBLEM: I tried many different email addresses but they are all invalid. Solution: make sure the email addresses you try are lowercase.
Did you use capital letters? It won't accept addresses with capital letters in but for some reason that's only mentioned on a dark corner of the forum and not the installer.
use lowercase.. also this format did cause error for some guys xxx.xxx@xxx.xxx - a trailing " . " before @
It wont let you use xxx+xxx@xxx.xxx with the "+" either. Rather annoying being a valid address and all, but easy enough to work around.