I want to use Thunderbird as a one-off back up of my source email folders. On Thunderbird PC, I have done this under Fetching mail settings with "Folder Poll Frequency" set to Never. On Thunderbird Desktop Account settings are different. On Server settings, I have unchecked for new messages, but they are still coming through. Any advice how to stop the messages synchronising from the source email system? I will then delete a lot of old messages on the source system, knowing they are available on Thunderbird desktop