LARGE ARCHIVE → SMALLER MBOX FILES
A smaller file.
The complete conversation.
Split a large mailbox into parts of 250 MB or less. Every email stays intact, including its attachments. Nothing is uploaded.
Reads a little at a time.
Keeps your original unchanged.
YOUR OUTPUT FILES
Whole messages. Original bytes.
The splitter scans the archive first, then lets you save the parts. It preserves the original message order and copies the email data without reformatting it.
If a single email is larger than your selected cap, splitting stops with a clear explanation. It will never cut an email or silently drop its attachments.
Recommended for large archives in desktop Chrome or Edge. Choose a folder with enough free space for a second copy of your archive. Keep the original file in place until saving finishes.
No upload, no account data.
Scanning and saving happen in your browser. This tool does not send or store your emails on a server.
Emails stay together.
Each part is an MBOX file with complete messages and attachments. Inaccurate size headers are checked against message boundaries. Uncertain boundaries stop the split.
Convert one part at a time.
Open a part in the PDF converter to create its PDF. Sent-date sorting happens within each PDF, not across the separate parts.
Large archives and format compatibility
The splitter reads in small blocks, so it does not need to load a multi-gigabyte archive into memory. Processing time depends on your disk and browser. There is no fixed input-size cap; available disk space and browser limits still apply.
Common mboxo, mboxrd, mboxcl and mboxcl2 exports are supported, including Vault-style separators and LF, CRLF or CR line endings. Content-Length is honored only when its target matches a verified message boundary or the end of the archive. If it is inaccurate, the splitter checks separators and email headers instead and shows a recovery notice. Malformed MBOX files can be ambiguous, especially if a mail exporter fails to escape a “From ” line in the body. Keep your original archive and review the parts. This splitter does not repair or certify emails.
A 250 MB input allowance in the PDF converter is not a guarantee that every 250 MB archive can render on every computer. If PDF preparation struggles, split into 100 MB or 250 MB parts.
Standalone offline edition. All processing stays on this device.