PST Rescue

PST to MBOX: move your Outlook mail into Thunderbird

Updated November 2026

Short answer: Thunderbird can't read a .pst file by itself. Convert the .pst to .mbox (one mailbox file per folder), then import those mailboxes into Thunderbird or Apple Mail. You don't need Outlook for either step.

Why Thunderbird won't import your .pst

Thunderbird's built-in Outlook import doesn't read the .pst file. It asks Outlook for the mail, so it only works on a PC where Outlook is installed (Mozilla Bugzilla 297533, Mozilla Support). Other archiving tools hit the same wall: one user found MailStore Home reporting "This feature requires Microsoft Outlook" for a .pst on a PC without it (Mozilla Support).

.mbox is the plain mailbox format Thunderbird and Apple Mail use. Once your mail is in .mbox, no Outlook is involved.

Step 1: Convert the .pst to .mbox

With PST Rescue on Windows:

  1. Open the .pst (or .ost) file. Check the folders and a few messages look right.
  2. Choose Export folder, then the folder you want or "The whole file".
  3. Tick .mbox mailboxes. Tick .eml files and Attachments too if you want loose copies.
  4. Choose an output folder and press Export. You get one .mbox file per Outlook folder, laid out like your Outlook folders.

The first 50 messages are free, so you can test the import end to end before buying Pro ($29 once) for the rest.

Get PST Rescue from Microsoft Windows 10 and 11

Free alternative for technical users: readpst from libpst writes mbox from the command line (libpst); on Windows it runs in WSL.

Step 2a: Import into Thunderbird

Thunderbird needs the free ImportExportTools NG add-on to import .mbox files (addons.thunderbird.net).

  1. In Thunderbird, install ImportExportTools NG from Add-ons and Themes.
  2. Right-click Local Folders (or any folder), choose ImportExportTools NG, then the mbox import command.
  3. Pick the .mbox files PST Rescue made. Each becomes a folder.

Want the mail in Gmail or another online account? Add that account to Thunderbird and drag the imported folders into it.

Step 2b: Import into Apple Mail

Copy the exported folder to the Mac, then in Mail choose File > Import Mailboxes, pick "Files in mbox format", and select the folder. Imported mail appears under an Import mailbox you can rename or move.

Or use .eml files

.eml is one file per message. Thunderbird, Apple Mail and new Outlook can open .eml files, which is handy for a few important messages. For whole folders, .mbox is quicker to import.

Questions

Are attachments kept in the .mbox?

Yes. Attachments stay inside each message. Tick Attachments in the export if you also want them as separate files in folders.

Does PST Rescue upload my mail to convert it?

No. The conversion runs on your PC. Nothing about your mail is sent anywhere.

Can I convert a corrupt .pst?

PST Rescue reads healthy files only; it doesn't repair damaged ones. Open the file for free first to see if it reads.

Will dates, senders and read status come across?

Dates, senders, recipients, subjects, bodies and attachments are kept in each message. Outlook-only details such as flags and categories may not survive in another mail app.

More: How to open a .pst file without Outlook · What new Outlook supports for .pst files