Hello,
Following communication with Auth0 Support, I can confirm this feature is not configurable and is not documented.
I have submitted feedback for this to be documented and potentially configurable for non-production environments.
Pending documentation, I have been informed the current email domain blacking listing includes:
'user.com',
'test.com',
'abc.com',
'example.com',
'test.com',
'b.c',
'1.com',
'11.com',
'2.com',
'3.com',
'4.com',
'a.com',
'test.be',
'test.dk',
'nope.com',
'abcdefg.com',
'nowhere.com',
'something.com',
'www.www'