Thunderbird provides the ability to archive messages - that is, to move them from the default folders to archive folders without deleting the messages altogether. This makes it easy to organize archives or move them to a backup device, and keep the Inbox clean. Messages can only be archived manually, not automatically. Archived messages are indexed by Thunderbird's search.
How do I archive my messages?
To archive one or more messages, select the desired messages and then click on the Archive button, or simply press A on your keyboard. It is recommended that you not select more than 2,000 messages at a time.
How do I configure archiving?
Configure archive location
The location of archived messages can be configured individually for each email account. In ToolsEdit > Account Settings, select the desired email account in the left panel, and then select the Copies & Folders setting. In the Message Archives section, use the settings in Keep message archives in to set the desired location.
Configure archive folder structure
You can define the structure of the archive folder by clicking the Archive options... button.
Then you can choose if you want to use a single folder for all your archives, or define some sub-folders, as indicated in the animation below: