When you request a Reset Password email to be sent a hidden security token is generated and this enables us to be sure that when we receive your request to create a new password that it is coming from the email address that was issued the Reset Password email.
When you request a Reset Password email you will need to use the latest email that was sent as any previous Reset Password email will no longer be valid.
If you are unsure simply request a new Reset Password email and use the corresponding email only.