This might not be relevant but if you are presently a BTBroadband customer and have a BTMail email account it will be "down graded" to a BTMail Basic account which can not be used with an email app or email client if you move to any other ISP other than EE.
If you wanted to retain the ability to use an email client or app you would need to pay £7.50 per month for a BT Premium email account.
If you are a new customer to BT they no longer offer an email service to new customers.