Linked email address might no longer belong to you
Some email providers periodically delete inactive accounts so that the username is available for others to use. To keep your Google Account secure, we want to make sure that all of the email addresses linked to your Google Account still belong to you.
For example, if you create an email account with the username email@example.com, Hotmail will recycle the email address if you haven’t used it in a while. The username john.smith will then be available for others to use as their Hotmail address. However, if firstname.lastname@example.org is still listed on your Google Account as your recovery email address, it could receive any password reset links you request and could be used to access your account.
To keep your account secure, we might ask you to verify ownership of a linked email address if we detect that it might no longer belong to you.