Unwanted Notifications

I use K-9 on Android 13 and T-Bird on Windows 10, IMAP. When I open an unread mail in T-Bird, I get a notification in Android. Is this intended behaviour? Can I turn it off?

Thanks

What notification do you get? Could it be that T-Bird moves the mail to different folder which is synched by K9 and hence gets a new notification? What email provider do you use? Which version of K9 do you use?

Thank you for your reply. It might be due to your suggestion re T-Bird moving mail.

I will monitor what goes on and return should this not be the case.