Hi George Yes there's no problem using both desktop and mobile versions. They can co-exist. Imap is designed to sync multiple clients. The mobile app asking you to sign-in to your google account is normal. This is the oAuth 2.0 authentication mechanism, a modern and more secure sign-in method for email apps. Many email providers now require this method which replaces traditional user name and password sign-in by apps. When you sign-in to google, you'll be prompted to give permission, allowing Thunderbird for Android access to you're emails. Once granted, TBA receives an oAuth authentication token from google which it uses to access your emails, rather than your user name and password.