The most popular tool to Import Outlook OST to Thunderbird is the eSoftTools OST to MBOX Converter This tool is specially designed to repair and convert OST files into Thunderbird Format without losing internal data. It’s easy to use by every user. It can convert OST files into multiple formats like PST, EML, EMLX, MSG, MBOX, HTML, Gmail, and many others.
Read More:- Import Outlook OST to Thunderbird
Step 1: Make Outlook your default program for sending/receiving emails. Go to the Start button and click Default Programs >> Set your default programs.
Step 2: Select Outlook from the Programs tab and click Set this program as default. Then click OK to save the changes.
Step 3: Now, launch Thunderbird and click on the Display the Thunderbird Menu option.
Step 4: Go to Tools >> Import.
Step 5: Select Mail or you can select the Import Everything option and click Next.
Step 6: Select Outlook as the file type and click Next.
Step 7: In the last window, click on the Finish button to complete the import process.
This will import all mails in the Outlook email client to the Thunderbird interface.
Hope This Works,
Peter