PST to MBOX — Outlook mail to Thunderbird or Apple Mail
Convert a .pst mailbox into a single mbox file that Thunderbird and Apple Mail import directly.
About this conversion
This is the conversion people look for when they leave Outlook: a .pst holds everything, but only Outlook opens it, while the rest of the world reads mbox. The whole mailbox is read here, in the page, and written back out as one mbox file.
What the mbox file looks like inside
One file with every message one after another, each starting with a “From ” line — the way Thunderbird and Apple Mail store mail themselves:
From anna.rees@example.com Mon May 03 09:12:00 2021 From: Anna Rees <anna.rees@example.com> To: Accounts <accounts@example.com> Subject: Invoice 1042 Date: Mon, 03 May 2021 09:12:00 +0000 … From accounts@example.com Fri May 07 16:40:12 2021 From: Accounts <accounts@example.com> …
Into Thunderbird
Install the free ImportExportTools NG add-on, right-click a folder under Local Folders and choose to import an mbox file. Or close Thunderbird and copy the file, without an extension, into the Local Folders directory of your profile — it shows up as a folder at the next start.
Into Apple Mail
Choose File → Import Mailboxes, pick “Files in mbox format” and point it at the file. The messages arrive in a new mailbox called Import, from where they can be dragged anywhere.
Just want to look inside it?
The same tool without converting anything: open a .pst file and read it.
You are not locked into MBOX
The file is parsed once and stays open, so the format is picked at the end rather than the beginning: the same .pst can leave here as CSV, XLSX, ZIP, EML, PDF, HTML, TXT or JSON. Before that you can search it by subject or address, filter by year, sender and attachment type, mark the duplicates and look through the archive overview.
Questions
- Which programs will open the result?
- Thunderbird and Apple Mail both import mbox directly. Outlook does not read mbox at all, so if the mail has to end up there, convert to separate .eml files instead and drag them into an Outlook folder.
- Are attachments kept?
- Yes. Each message is written out complete, with its attachments inside, exactly as mail normally travels.
- How large a .pst can I convert?
- The file is read in pieces straight from disk, so size is not the limit — mailboxes of several gigabytes open.