Outlook Mobile Password Requests and revoked security tokens
After some considerable time - and a lot of messages - Microsoft support are now adamant that the reason their Outlook Mobile app keeps asking for BT Mail passwords, and latterly IMAP information, to be re-entered regularly is because the security token issued to the app is being revoked by the BT Mail system. They say they do not know why this is happening and - as I guess I expected - referred my to BT Mail admins.
This seems to happen at random. I started to wonder if it was happening because I had BT Mail access configured on different devices and it was reacting to multiple connection requests by revoking the access token. I'm still investigating that but in the meantime it would help enormously if someone with access to BT Technical could tell us why BT Mail would be revoking access tokens.
It appears to be a security issue but it could be a consequence of the long awaited migration from the BT Yahoo servers. In case anyone asks my webmail says I'm still on BT Yahoo.