Hmm, sorry but I don't buy that the "correct way to validate" is not to validate the input. Email addresses aren't a special enough case to be handled differently than any other user input, which we always validate to both sanitize and show client-side errors, if nothing else. Sure, the complete regex is complex, but it is defined and is hardly unconquerable. Look at Django's `EmailValidator` implementation for examp…
Regarding that testdata, what is the reason for rejecting bare IP literals on the right hand side? It seems pedantic to require the square braces.
That part is confusing to me.
I ran a fresh install of Django to confirm and it behaves as you suggest.
Edit: Perhaps only for low digits. Hmm.
>>> from django.core.validators import EmailValidator
>>> e = EmailValidator()
>>> e.__call__('foo@[1.2.3.4]')
>>> e.__call__('foo@1.2.3.4')
ValidationError: [u'Enter a valid email address.']
>>> e.__call__('foo@0.0.0.0')
ValidationError: [u'Enter a valid email address.']
>>> e.__call__('foo@[0.0.0.0]')
>>> e.__call__('foo@10.10.10.10')
>>> e.__call__('foo@[10.10.10.10]')
>>> e.__call__('foo@255.255.255.255')
>>> e.__call__('foo@[255.255.255.255]')