plainfolder → Mail → OST
Open an OST file without Outlook or the original account
An .ost is the copy Outlook keeps on your disk. Drop it here and the messages come back — no account and no Exchange needed.
No server processing
No account
No daily limits
What a .ost file is
Outlook keeps an .ost so it can work while the network is down: the same structure as a .pst, tied to one mailbox. When that mailbox is gone, Outlook will not open the file at all, which is exactly when people need what is inside it.
This is the file left over after a job ends, an account is closed or a server is retired. Desktop converters treat it as a paid feature; online ones ask you to upload a complete mailbox. Neither is necessary — the reading happens here, in the page.
What you can do here
Read and searchOpen the file, search by subject, address or text, filter by year, sender and attachment type.
Take things outSave every attachment as one zip, or the messages themselves as separate files.
Keep a copyCSV, XLSX, ZIP, EML, MBOX, PDF, HTML, TXT, JSON — whichever format outlives the one you have.
Convert OST to something else
Questions
- Do I need the account the file belongs to?
- No. The messages are read out of the file itself.
- Does the newer Outlook format work?
- Yes. Outlook 2013 and later write 4 KB pages with compressed blocks; both that and the older layout are read.
- Is anything sent to a server?
- No. Nothing is uploaded, and there are no accounts here to sign in to.
- Can I convert it to something I can keep?
- Yes — a CSV table of the messages, separate .eml files, or PDF through the print dialog.
- Will a large .ost work?
- Yes. The file is read in pieces, so a multi-gigabyte offline file opens without being loaded into memory.