How to Import OST to Thunderbird
In short: To import OST to Thunderbird, know that Thunderbird cannot open an OST or a PST, so exporting to PST does not help. If Outlook still has the profile, Thunderbird’s Import from Outlook reads it live. Otherwise, convert the OST to MBOX or EML, then import that with the ImportExportTools NG add-on. A tool can also send an OST straight into Thunderbird, including orphaned files.
Why importing an OST is not direct: the PST myth
Clear this up first and you save real time. An OST is an Outlook offline cache that Thunderbird has no way to read. The trap in many guides is the advice to export the OST to a PST and open that in Thunderbird. Thunderbird cannot open a PST either, since a PST is just as much an Outlook format as an OST. So the PST route is a dead end. What does work is one of two things: if Outlook is installed with the account’s profile, Thunderbird can read that profile directly. If not, you convert the OST into a format Thunderbird understands, which is MBOX or EML.
Technical Executive and Staff Writer, Corbett Software
“The PST step is where people get stuck, because Thunderbird cannot open a PST at all. If Outlook has the profile, use Import from Outlook, which reads it live. If not, convert the OST to MBOX and bring it in with ImportExportTools NG. For an orphaned OST, a converter is the clean way.”
If Outlook has the profile: Import from Outlook
When Outlook is installed on the same PC with the account set up, Thunderbird can pull the mail from that live profile, with no file in between.
- Make sure Outlook is set up with the account and has synced, so the OST is current.
- Open Thunderbird, click the menu, then Tools, then Import.
- Choose Import from Outlook, then select mail, then continue.
- Thunderbird reads the live Outlook profile and brings the folders in.
This works only while Outlook holds the profile. For an orphaned OST or a PC without Outlook, use the convert route below.
Convert the OST to MBOX or EML, then import
This is the reliable route, because it gives Thunderbird a format it truly reads.
- Convert your OST to MBOX or EML with an OST converter, which reads the file even without Outlook.
- In Thunderbird, add the ImportExportTools NG add-on from the Add-ons manager.
- Right-click a local folder, choose ImportExportTools NG, then import the MBOX file. You can also import all EML messages from the folder.
- The mail lands in Thunderbird with its folders intact.
Send an OST straight to Thunderbird with a tool
To skip the two steps, a converter can write the OST directly into Thunderbird, handling orphaned files too.
The Corbett OST Converter reads an OST directly, with no Outlook needed, then exports it straight to Thunderbird, to MBOX or to EML, keeping folders and attachments. It opens orphaned and inaccessible OST files, so a filter lets you move only a date range or folder. A free demo edition lets you preview the mail first and runs on every edition of Windows.
- Install and open the tool, click Open, choose Email Data Files, then OST Files, then select your OST.
- Preview the folders and mail.
- Click Export, choose Thunderbird, apply any filter, then Save.
Frequently asked questions
Can Thunderbird open an OST file directly?
No. Thunderbird cannot read an OST. Use Import from Outlook if Outlook has the profile. Otherwise convert the OST to MBOX or EML and import that with ImportExportTools NG.
Can I export the OST to PST and open it in Thunderbird?
No, this is the common mistake. Thunderbird cannot open a PST either, since a PST is an Outlook format. Convert the OST to MBOX or EML instead, which Thunderbird reads.
What does Import from Outlook actually import?
It reads a live Outlook profile installed on the same PC, not a file you browse to. So it works only when Outlook still has the account and its OST.
How do I import an orphaned OST into Thunderbird?
Import from Outlook will not work, since there is no live profile. Convert the orphaned OST to MBOX or EML with a converter, then import it with ImportExportTools NG.
Do I need the ImportExportTools NG add-on?
You need it to import MBOX or a folder of EML files into Thunderbird. A tool that exports an OST straight to Thunderbird can skip the add-on.
Does this change my original OST file?
No. Every route here only reads the OST. The original file stays as it is, so the mail lands in Thunderbird as a copy.