PST to MBOX

Convert your Outlook PST file(s) into a single mbox archive that can be imported by Thunderbird, Apple Mail, or any command‑line mail tool. The tool preserves every message’s headers, body (including HTML), and attachments, and always produces one file called output.mbox regardless of how many PSTs are uploaded. — scope: only messages are kept; folder hierarchy is flattened —

Headers and metadata

All standard email headers from each Outlook message are copied into the mbox entry. From, To, Cc, Subject, Date and Message‑Id appear exactly as stored, letting mail clients recognise the original identity. The mbox separator line includes the sender address and the original date in the classic “Day Mon DD HH:MM:SS YYYY” format.

Message bodies and formatting

HTML bodies are transferred unchanged, preserving paragraphs, headings, tables, inline styles and any Unicode characters. Plain‑text bodies are kept as plain‑text MIME parts. If a PST message contains both an HTML and an RTF‑only body, the converter keeps the HTML version; RTF‑only formatting is omitted.

Attachments and inline resources

Every binary attachment stored in a PST becomes a base64‑encoded MIME part inside the mbox, so PDFs, Word files, images and other documents are reconstructed exactly when the archive is imported. Inline images retain their Content‑ID references, allowing clients to display them inline. External image URLs stay as the original HTTP/HTTPS links.

Flattened folder structure and single output file

All messages from all uploaded PST files are concatenated into one file named `output.mbox`, regardless of the number of PSTs or folders. The converter walks each PST’s folder tree in depth‑first order and writes each message to the linear mbox stream, discarding original folder names. Users who need to preserve hierarchy should use a PST‑to‑EML conversion instead.

Limits and scope

Upload size limit

Anonymous users have a lower upload cap; signed‑in users get a higher limit.