Asking to get read/write access on my GMail box right away is a non-starter for me. I get that it may help you auto-populate my database, but you really should avoid asking it without any proper popup explaining why you must have this authorization.
Ideally you should use a two-step authorization phase, basic-info only for login/registration, then once the user gets to see the interface, have a button to extend permissions to read GMail.
Ideally you should use a two-step authorization phase, basic-info only for login/registration, then once the user gets to see the interface, have a button to extend permissions to read GMail.