Hi Richard

Emails are synchronised between your phone and your account providers server, not with Thunderbird on your desktop computer. There are two protocols the app can use to connect with the server, IMAP and POP3.

I suspect your using the old POP3 method. Please confirm!

You can check this on your phone's Thunderbird app under settings > account > fetching mail > incoming server. The combination of server name and port number determine which protocol is used.

IMAP is the modern and recommended method.

1. Emails are stored on the server.
2. Client apps synchnonise to show the same set of emails as the server holds.
3. Supports folders
4. Changes on the phone app (such as deletions) are applied to the server.

POP3 is an old legacy way.

1. Client apps download a "local only copy" of emails.
2. They are typically deleted from the server after the client downloads them.
3. Changes such as deletions, folder management etc only apply on the clients local copy.
4. Changes in one client don't synchnonise with other clients

Thanks for reply. Will check w server technician at Skybest. But I believe it is an IMAP setting. Will get back to you in the next several days after talking to server tech. The system worked perfectly w previous phone and everything properly synced. So must be setup issue on new phone will advise. Again thank you for time and response. This is very frustrating to a old guy w limited tech skills.