Open an OST file — no Exchange connection needed
Drop an Outlook .ost cache file and browse, read, and search it right here. The file is parsed on your own machine with no server connection and no Outlook — it never leaves your device.
Drop the .ost file — it is read locally, nothing is uploaded.
Browse the folder tree and open any message with its attachments.
Search every folder by subject, sender, or body text.
Export a single message free, or unlock batch conversion with a license.
Open an OST file — no Exchange connection needed
An OST is the offline cache Outlook keeps for an Exchange or Microsoft 365 mailbox, and Outlook refuses to open one unless it can verify the original account — which makes a perfectly healthy backup unreadable the moment the account is gone. Mailward reads the OST format directly, the same way it reads PST, so mailbox data you are entitled to stays accessible: folder tree, messages, attachments, and full-text search, all parsed locally in a Web Worker.
Reading and single-message export are free; batch conversion is the paid step. Make sure you have the right to access the mailbox data before opening a file that is not yours.
Before you trust a mail file to a website
Q. Do I need the original Exchange account?
No. Mailward reads the OST file directly on your device — no server connection, no account verification, no Outlook. Only open files whose mailbox data you have the right to access.
Q. Is an OST different from a PST?
They share most of their internal structure. A PST is a standalone archive you export on purpose; an OST is the offline cache Outlook maintains for a connected account. Mailward reads both.
Q. Will my mailbox be uploaded anywhere?
No. The file is read with the browser's File API and parsed in a Web Worker on your machine. You can disconnect from the network after the page loads and keep reading.
Q. Can I turn the OST into something other apps read?
Yes — with a license you can batch-convert folders to MBOX or EML, the open formats Thunderbird, Apple Mail, and most clients import. Single-message EML export is free.
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.