Letterlark
EN
EnglishEspañolPortuguêsFrançais

Open and search MBOX files

An .mbox file is a whole mailbox in one file – Google Takeout exports Gmail this way, and Thunderbird and Apple Mail use it too. Letterlark opens .mbox files of any size in your browser so you can read and search them without importing them into a mail program.

Open Letterlark – free viewer

Steps

  1. Open Letterlark.
  2. Drop the .mbox file onto the page (a Google Takeout file is usually called All mail Including Spam and Trash.mbox).
  3. Search by sender, subject, text or attachment name; filter by date or “with attachments”.
  4. Export what you need: PDF, EML files, a smaller MBOX, a CSV list or all attachments as a .zip.

Big archives

Letterlark reads the file in chunks and keeps only an index in memory, so archives of several gigabytes can be opened. The first pass reads every message to build the search index; you can start reading while the progress bar runs.

Character sets

Each message is decoded with the charset it declares (UTF-8, ISO-8859-x, windows-125x, KOI8-R, Shift_JIS and others), and right-to-left text is displayed right-to-left.

Questions and answers

Is my Google Takeout archive uploaded?

No. The file is read by your browser on your computer. The app cannot open network connections.

Can I split a large MBOX?

Yes: filter or select part of the messages and export them to a new MBOX file. Without a license each export holds up to 20 messages.

Last updated: 2026-10-26