If you want to import Outlook data file to Thunderbird, then you can use manual as well as automated solutions.
For manual process, follow these steps :
- Set Outlook as your default email client
- Open Thunderbird. Click on Tools » Select Import option.
- Select Mail from the options » Click Next.
- Choose Outlook and click on Next.
Click Finish after completion of the process.
The main problem with manual process is that it needs both Outlook and Thunderbird to be installed in same machine.
Another alternative to import Outlook data file to Thunderbird is using a converter tool. Try Outlook to Thunderbird Converter from Tools2Export and get easy, instant and accurate solution to batch import Outlook emails to MBOX and access in Thunderbird, Apple Mail, SpiceBird, OperaMail, PocoMail, The Bat and many other email clients.