thepracticalparanoid.com
Q: What can I do if I have someone's Gmail account username? - The Practical Paranoid
A: Nothing. Fundamentally all you have is an email address. If you were interested in committing a felony, you could attempt to hack into their Google account. But assuming the user has a strong password and has enabled Two-Factor Authentication, it would be a futile attempt at state-funded housing.
Marc Mintz