The image mentions the 'All Mail' folder. Gmail stores all of it's emails - incoming, outgoing and archive - everything in the 'All Mail' folder. Gmail undertands that 'view' is not exactly very useful, so they invented 'labels'. When a 'label' eg: Inbox - which is like a type of tag is applied to the email in 'All Mail' folder, it can display a virtual copy in the server Inbox label. This means it's possible to apply more than one label to any email so it can display in more than one 'label'. Thunderbird has no knowledge of 'labels', so it downloads whatever is displayed in the 'Inbox' or any other server label and stores it in what Thunderbird calls 'folders'. These downloads are stored as separate copies. If you subscribe to see the 'All Mail' folder then basically a complete copy of everything you already have displayed in all other folders. When you delete an email and put it into the server 'Trash' folder, gmail will auto delete it off server after 30 days and will also auto delete it from the 'All Mail' folder. If you directly delete anything from the 'All Mail' folder via Thunderbird then it will get deleted off server, so all labels get removed by default meaning that copy in eg: Inbox will also get deleted because it no longer exists. You do not need to move anything from the gmail Inbox into the 'All Mail' because if it's not in 'All Mail' then it does not exist and will not display in any folder. Basically, you should not be putting anything in 'All Mail' nor deleting from 'All Mail'. Anything you 'Archive' just means gmail removes all labels, so email now only resides in 'All Mail' by default. This means it's very difficult to locate archived emails, advise is to create an 'Archives' folder/label and adjust the Account Settings > Copies & Folders to use that 'Archives' folder on gmail account. It means gmail will apply a new label so you can see it in 'Archives'. I would advise you to not subscribe to see the 'All Mail' folder. In Folder Pane * Right click on gmail mail account name folder and select 'Subscribe' * Select the 'All Mail' folder * click on 'Unsubscribe' * click on 'OK'. It is just a duplicate of everything and can be a very large folder. If you delete any email from eg: Inbox, then it also means that 'All MAil' folder will also need to resynch as it's also updated. It may also mean you need to compact that large file more frequently to remove old marked as deleted and hidden emails. If that 'All Mail' folder gets corrupted in Thunderbird then you may end up losing all your emails in one go. Corruption can occur for various reasons - lack of compacting - or if your Anti-virus decided it contains something it does not like and attempts to fix it etc or if computer crashes whilst file is being used. It's just a matter of risk and whether it's worth that risk just to see a duplicate of everything.