OST to MBOX

Convert an Outlook .ost file into one .mbox file that includes every message from all folders, keeping full headers and MIME‑encoded attachments. The resulting file can be imported directly by Thunderbird, Apple Mail and most command‑line mail tools. ⚠️ Scope: the converter works with standard Unicode OST files; very old non‑Unicode OSTs are outside its coverage.

Single‑file archive of all mail

The converter reads every email stored in a standard Unicode Outlook .ost file and writes them sequentially into one .mbox file (output.mbox). This single archive can be opened directly by Thunderbird, Apple Mail, and common command‑line mail utilities, allowing the whole mailbox to be imported in one step.

Complete headers and bodies

For each message the original From, To, Cc, Subject, Date, Message‑Id and any other standard headers are reproduced in the MBOX entry, so importing clients preserve sender, recipients and ordering. HTML bodies retain their markup and links, while plain‑text bodies remain unchanged.

Attachments and inline resources

All file attachments are included as MIME parts within the same MBOX entry, encoded as required. Inline images embedded via CID references keep their identifiers, ensuring they display correctly after conversion.

Supported OST scope

The tool works with standard Unicode Outlook .ost files created by recent Outlook versions. Very old non‑Unicode OST files are outside its coverage. For those legacy archives, a separate conversion path (e.g., OST → EML) is needed.

Limits and scope

OST format scope

Supports standard Unicode Outlook .ost files; very old non‑Unicode OSTs are outside the tool’s coverage

Output format

Produces a single .mbox archive regardless of the number of messages