Import data from Outlook into Thunderbird on Windows
Import all Outlook data
Click on the three vertical lines, then select Tools, then Import.
Select the import source from Outlook and click on the Continue button.
Choose the items you wish to import and click the Continue button.
In the final confirmation step, you’ll see a summary of your choices. Click the Start Import button to finalize the import, or the Back button to perform changes.
Import Mail Only from Outlook
Click on the three vertical lines, then select Tools, then Import.
Select the import source from Outlook and click on the Continue button.
Choose Mail Messages and click the Continue button.
Click the Start Import button to finalize the import. Click Finish.