There are more than 4 million people who use iPhone to access their mail. There iPhone or any Mac device is synced with Gmail .it does happen sometimes that you are logged in for a long time and you tend to forget the username and the password of the Gmail account linked with your iPhone to Gmail. Below login there will be a hyper link where you have to select reset password. A new page shall pop up where there will be a two step verification. A new link shall be sent to your iPhone account and you will be able to use it again.
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