Most of the emails I get claiming to be from BT are scams. Some are really obvious - particularly where there is bad grammar. Some are more subtle - I have even seen ones that are almost exactly the same as genuine BT emails - they have copied the whole of an email and just changed the links.
Be suspicious. If in doubt, hover your mouse over any links they want you to click. They should all go to domains ending in "bt.com", or possibly "custhelp.com" for help information. If it's anything else, it's probably fake.