Add-ons
About this Add-on
## How to use FolderSync
FolderSync copies missing email messages between two Thunderbird folders. It can synchronize folders from different email accounts or two different folders within an account.
### Create a synchronization
1. Click the **FolderSync** button in the Thunderbird toolbar.
2. Select **+ New Synchronization**.
3. Enter an optional name for the synchronization.
4. Under **Folder A**, select the first account and folder.
5. Under **Folder B**, select the second account and folder.
6. Choose the synchronization direction:
- **A ↔ B (Bidirectional):** Missing messages are copied in both directions.
- **A → B:** Missing messages are copied from Folder A to Folder B only.
- **B → A:** Missing messages are copied from Folder B to Folder A only.
7. Optionally enable automatic synchronization and enter an interval between 1 and 1440 minutes.
8. Click **Save**.
### Run a synchronization
Click **Start sync** next to a saved configuration. FolderSync compares the messages in both folders and copies the missing messages according to the selected direction.
The status card shows the current progress, the result of the last synchronization and the number of copied messages.
### View errors and diagnostic information
Click **Log** on a synchronization card to view its activity and any errors. The log can be cleared at any time.
### Edit or remove a synchronization
Use **Edit** to change a saved configuration. Use **Delete** to remove it. Deleting a configuration does not delete any email messages.
### Important behavior
- FolderSync copies messages; it does not move them.
- Deleting a message in one folder does not delete it from the other folder.
- Messages are matched primarily by their Message-ID to prevent unnecessary duplicate copies.
- The destination folder must allow messages to be added.
- Automatic synchronization runs only while Thunderbird can execute the extension's background tasks.
### Privacy
FolderSync does not send email data to the developer or to third-party services. It works through Thunderbird's built-in MailExtension APIs. Depending on the configured email accounts, copied messages may be uploaded to the destination account by Thunderbird.
FolderSync copies missing email messages between two Thunderbird folders. It can synchronize folders from different email accounts or two different folders within an account.
### Create a synchronization
1. Click the **FolderSync** button in the Thunderbird toolbar.
2. Select **+ New Synchronization**.
3. Enter an optional name for the synchronization.
4. Under **Folder A**, select the first account and folder.
5. Under **Folder B**, select the second account and folder.
6. Choose the synchronization direction:
- **A ↔ B (Bidirectional):** Missing messages are copied in both directions.
- **A → B:** Missing messages are copied from Folder A to Folder B only.
- **B → A:** Missing messages are copied from Folder B to Folder A only.
7. Optionally enable automatic synchronization and enter an interval between 1 and 1440 minutes.
8. Click **Save**.
### Run a synchronization
Click **Start sync** next to a saved configuration. FolderSync compares the messages in both folders and copies the missing messages according to the selected direction.
The status card shows the current progress, the result of the last synchronization and the number of copied messages.
### View errors and diagnostic information
Click **Log** on a synchronization card to view its activity and any errors. The log can be cleared at any time.
### Edit or remove a synchronization
Use **Edit** to change a saved configuration. Use **Delete** to remove it. Deleting a configuration does not delete any email messages.
### Important behavior
- FolderSync copies messages; it does not move them.
- Deleting a message in one folder does not delete it from the other folder.
- Messages are matched primarily by their Message-ID to prevent unnecessary duplicate copies.
- The destination folder must allow messages to be added.
- Automatic synchronization runs only while Thunderbird can execute the extension's background tasks.
### Privacy
FolderSync does not send email data to the developer or to third-party services. It works through Thunderbird's built-in MailExtension APIs. Depending on the configured email accounts, copied messages may be uploaded to the destination account by Thunderbird.
