100% not a genuine email, check the sender email....
Learn more about protecting yourself from scams :
Handling scam emails
As already stated, it is a scam.
BT do not use gmail addresses to send out emails.
If you suspect an email as being a scam it invariably is. If you have any doubt do not click on any links contained in the email. Log onto your MyBT account using your normal trusted route and you can view your bill there.