Convert your email exports between mbox and EML
Drop a Google Takeout export or a handful of .eml files and get the other format back, in a zip. Nothing is added, nothing is removed — only the container changes.
How it works
- Drop your files — one or more mbox, one or more EML, or a mix of both. Each file's format is recognised by reading its first bytes.
- Pick the output format — one .eml file per message, or a single mbox gathering everything.
- The conversion starts straight away — no volume to approve, no payment, no account: the tracking page shows live progress.
- Download the archive — a .zip available for 48 hours from the tracking link, then deleted for good.
What changes, and what does not: headers, body, attachments and encodings are copied byte for byte. Only the container moves. For mbox output, each message is preceded by its "From" line, and body lines starting with "From" get a leading angle bracket (the mboxrd convention): without that precaution an innocent sentence would become a message boundary, and your file would count more messages than it really holds.
The .eml file names are built by us: a five-digit sequence number, then the message subject reduced to letters, digits and spaces. That is deliberate — a file name taken verbatim from an unknown message is a classic attack vector against unzipping software.
Use cases
- Make a Google Takeout export usable — Takeout hands you a monolithic mbox of several gigabytes; splitting it into .eml files makes every message something you can handle on its own.
- Prepare an import into Thunderbird or Apple Mail — those clients expect an mbox. If what you have is a pile of .eml files, the reverse conversion gathers them into one ready-to-import file.
- Archive a handful of specific messages — pull the messages that matter out of a big mbox, as standalone files you can file away, attach or copy to an external drive.
- Merge scattered backups — several exports made on different dates, dropped together, come back out as a single mbox.
- Feed another tool — many analysis, indexing or search utilities read only one of the two formats. Converting means your tooling no longer has to be chosen by your export format.
- Put it back into a mailbox afterwards — the archive produced can go straight to the mbox / EML import, which pushes it into any IMAP mailbox.
What this tool doesn't do
- No PDF conversion. It would need a full HTML rendering engine to stay faithful to the message, and would remain very slow on a large export. We would rather not announce it than ship an approximate layout. To read a message, the EML viewer shows it on screen, and your browser's print dialog turns it into a PDF.
- No .pst, no .msg. These proprietary Microsoft formats are not mere containers: reading them correctly is a job of its own. A .msg dropped here is recognised and refused, with the steps to get an .eml out of Outlook.
- Gmail labels do not become folders here: the conversion only changes container. It is the import tool that recreates one folder per label, when the messages land in a mailbox.
- Duplicates are not detected. Dropping the same export twice produces the same messages twice in the output archive.
- A cap of 2GB and 50 files per conversion, the same for everyone. The server also caps uploads at around 8MB for now, while a hosting setting is being applied.
- The archive produced stays downloadable for 48 hours, then it is deleted for good. The files you dropped are deleted as soon as the conversion ends.
Frequently asked questions
What file formats are accepted? +
mbox files (the format of Google Takeout exports and of most Unix mail clients) and EML files (one message per file). The format is recognised from the file's content, not its extension: an mbox saved as .txt is accepted, and a PDF renamed to .mbox is refused with a clear message.
What is inside the archive I download? +
For EML output, one .eml file per message, numbered in reading order and followed by the message subject when there is one. For mbox output, a single messages.mbox file gathering every message from every file you dropped. Either way the archive is a .zip, available for 48 hours.
Are my messages altered during the conversion? +
No. Headers and body are copied as they are, attachments and encodings included. Only the container changes: the "From" line that separates messages inside an mbox is added or removed, and body lines starting with "From" are protected with a leading angle bracket (the mboxrd convention) so they are not mistaken for a message boundary when the file is read back.
Why is there no PDF conversion? +
Because we would rather not do it halfway. A faithful PDF means rendering the message's HTML, its embedded images and its layout — that is a full rendering engine, and across an export of several thousand messages it stops being "a few clicks". Until we can do it properly, we do not offer it. To read a message on screen the EML viewer already does the job, and your browser's print dialog produces a PDF.
Is there a size limit? +
The target limit is 2GB and 50 files in total per conversion, the same for everyone. In practice the server currently caps uploads at around 8MB while a hosting setting is being applied: beyond that the conversion is refused with a clear message instead of silently failing. In the meantime, split your export into smaller files and convert them one after another.
What happens to my files after the conversion? +
The files you dropped are deleted from our servers as soon as the conversion ends, whether it succeeded or failed. The archive produced stays downloadable for 48 hours from the tracking link, then it is deleted for good. No uploaded file is ever served back as-is: the only downloadable thing is the archive we built.
What about Outlook .pst or .msg files? +
They are not supported. These are proprietary Microsoft formats (an OLE container for .msg, a full database for .pst): reading them correctly takes far more than a change of container. A .msg dropped here is recognised as such and refused, with the steps to get an .eml out of Outlook.
Can I convert several files at once? +
Yes. Drop as many files as you like within the cap, mixing formats if needed: all their messages end up in a single output archive, in file order.