I'm also having problems with BTmail on Samsung/Android.
I had some issues before Christmas with clients on both PC and Android that were related to account locked.
They were resolved and my PC still works fine, but starting last week the Samsung/Android Outlook client misbehaves on a daily basis.
It continually asks me to re-enter my password, when I click "ok", it gives me the full configuration entry screen.
Re-entering all the details does no good and I get a sign in error.
I've tried the "do nothing" approach over several days, but it doesn't recover.
The only way out of this is to uninstall Outlook and re-install it. It's then fine for a day or so and then I get the password prompt again.
I have even done a factory reset of the S7, all apps and OS updated to latest - without success.
Either Yahoo, or Outlook have changed something and they no longer play well together.
I also run the Gmail client and the native email client on my phone accessing different services Gmail and another IMAP service) and they are fine. I have had no issues with them over several years.
Going to try a different client, but I am getting really frustrated with BT mail.
It was suggested I would be part of the new BTmail trial - I hope that is the case.