Over the last week or so when we send or receive messages they are no longer using our email aliases and are only displaying the main account of the email address.
firstname.lastname@example.org might have 2 aliases email@example.com and firstname.lastname@example.org but only sening and receiving as email@example.com. This is across our whole company.
You're best contacting the technical team about this on either telephone number 0800 800 154 or on livechat, available until 8pm, using this link: https://business.bt.com/help/contact-us-business/#fix-emailcomphosting-email
They will be able to make sure that the alias is set up correctly on your account.