Before:
    
        >>> email.message_from_string('From: a@malicious.org@important.com', policy=email.policy.default)['from'].addresses
        (Address(display_name='', username='a', domain='malicious.org'),)
    
        >>> parseaddr('a@malicious.org@important.com')
        ('', 'a@malicious.org')
    
    After:
    
        >>> email.message_from_string('From: a@malicious.org@important.com', policy=email.policy.default)['from'].addresses
        (Address(display_name='', username='', domain=''),)
    
        >>> parseaddr('a@malicious.org@important.com')
        ('', 'a@')




https://bugs.python.org/issue34155