Convert OST to MBOX — without Outlook
Move mail out of an Outlook .ost cache and into the open .mbox format that Thunderbird, Apple Mail, and Gmail imports understand. The conversion runs on your machine — nothing is uploaded.
Drop the .ost file — Mailward lists every folder without Outlook.
Convert one folder free, or the whole archive with a license.
Download the .mbox file, generated entirely in your browser.
Import it into Thunderbird, Apple Mail, or a Gmail migration.
Convert OST to MBOX — without Outlook
Use this converter when a mailbox only survives as an OST cache and you need it in a format other apps can read. Outlook itself will not export an OST it cannot verify against the original account, which strands otherwise healthy mail.
Mailward reads the OST directly in your browser and writes standard MBOX — converting a single folder is free, whole-archive export is the paid step. Everything runs locally in a Web Worker, so the mailbox never touches a server.
Make sure you have the right to the mailbox data before converting a file that is not yours.
Converting this file
Q. Does this need the original Exchange account?
No. The OST is read directly from the file on your device — no account check, no server connection, no Outlook install.
Q. Which apps can open the MBOX output?
Thunderbird (via ImportExportTools NG), Apple Mail (File → Import Mailboxes), and most Gmail or Google Workspace migration tools read MBOX directly.
Q. Is the conversion free?
Converting a single folder is free. Exporting the whole archive, or several files at once, is part of the one-time Pro license.
Q. Does my mailbox get uploaded?
No. The OST is parsed and the MBOX is generated in a Web Worker on your own machine. You can go offline after the page loads and the conversion still works.
Simple, one-time pricing
Opening, reading, searching, and single-message export are free forever. Batch conversion is a one-time unlock — no subscription, no recurring fees.
Everything you need to open and read an archive.
- Open & read PST, OST, MBOX, EML — locally
- Full-text search across every folder
- Export a single message
- Files never leave your device
Unlock batch conversion for good — a single payment, yours to keep.
- Batch-convert whole folders to MBOX or EML
- Export all search results as .eml files in one click
- Extract every attachment to a ZIP
- Lifetime license — no renewals
Other formats & archives
Same local-first engine, every common mail format.