I would like to suggest a feature to allow us to choose specific folders from being synced by the client. For example, “All Mail” and “Inbox” show duplicate emails in the conversation view, as they are present in both folders as a single email. Having the ability to choose not to sync “All Mail” would easily stop seeing duplicates.
You can’t not sync All Mail. That is where Google keeps all the messages.
The way they work is that messages only exist in that folder. Then they have tags (labels) that organise messages into virtual folders like Inbox and Sent.
If you disable the All Mail folder, you will have no messages anywhere in eM Client.