What Google is telling about this?
“Please be aware, residual copies of deleted messages and accounts may take up to 60 days to be deleted from our active servers and may remain in our backup systems. If you delete your Gmail address but wish to have it back, we work to help you recover your deleted accounts whenever possible. However, within a few weeks’ time, accounts are usually no longer retrievable. Note that a successful recovery will only recover the username associated with the account”. – GoogleFollow the link below to disable or remove Gmail mail service and username from Google account.
https://www.google.com/accounts/DeleteCaribouService – For deleting only Gmail account.
https://www.google.com/accounts/DeleteAccount – For deleting any Google product/service associated with your Google account.
While deleting Google may ask you reasons for who you are closing this account. Be careful to think again what you are doing before the action.