Having recently discovered the hard way that I was migrated (and had no BT e-mail for 3 days), I have now discovered that all the authorisations I had set up for sending of e-mail fwith the senders address being a non-bt account have gone.
The help files point me in the direction of setting up BT Mail to get non-bt mail for me. This is not what I want. All I need is to authorize andrew@******.org.uk as an authorised user on my BT account. Thunderbird is quite capable of getting the mail from mail.****.org.uk with POP3. I just need to be able to use the BT smtp server for outgoing mail only.