A complete, native MBOX toolkit
Everything you need to open, search, read and export huge email archives on Mac and Windows — without a web app in a window.
Built for scale
Any file size
A streaming parser with a 1 MB buffer opens files from a few KB to 50+ GB without ever loading them into RAM.
Instant re-opens
A binary index with SHA-256 validation makes every re-open take under a second, regardless of size.
Low memory footprint
Even a 50 GB archive stays under 600 MB of RAM thanks to on-demand streaming and an LRU message cache.
Repair damaged mailboxes
Deep-scan recovery re-detects lost message boundaries and exports a repaired copy — the original file is never modified. (Pro)
Find anything
Powerful search syntax
Use from:, to:, subject:, body:, date:, has:attachment, size:>, OR, negation and exact phrases — or the visual filter sheet.
Gmail labels
Reads Gmail labels straight from Takeout. Browse by label in the sidebar with live message counts.
Conversation threading
The JWZ algorithm groups messages into conversations with visual reply chains up to four levels deep.
Properties, MIME & Hex views
Three new ways to inspect a message: a Properties panel, the MIME part tree and a raw hex dump — ideal for technical or forensic work.
Get your data out
Export anywhere
Export to EML, CSV (Excel-ready, UTF-8 with BOM) or plain text, and extract attachments in bulk.
Export a selection as a new MBOX
Narrow a huge archive down by search, by Gmail label or by hand, and write the result to a brand-new mailbox that contains only those messages — the delivery step of a legal hold or a public-records request. The original file is never modified.
Merge & dedupe MBOX
Combine multiple MBOX files into one, with optional Message-ID deduplication. Export a single label as its own MBOX.
Attachments
View attachments inline, preview with Quick Look (Spacebar), save individually or in bulk, or drag straight to Finder (Explorer on Windows).
Export to PDF
Export any message to a self-contained, multi-page PDF with the same layout as printing. One message is free; batch export is Pro.
Export to HTML
Save any message as a self-contained HTML file with images embedded and attachments as downloadable links — it opens anywhere. One message is free; batch is Pro.
Native & private
Truly native on Mac & Windows
Native on Mac (SwiftUI + AppKit) and Windows (WinUI). Dark mode, drag & drop, system share, print and full keyboard navigation. No Electron, no Java.
Privacy by design
Everything runs locally. No cloud, no telemetry, no account. Remote images blocked and HTML sanitized by default.
Drag & Drop everywhere
Drop MBOX or EML files onto the app to open them, and drag messages out as .eml or attachments to Finder.
Search syntax at a glance
Combine prefixes, operators and exact phrases to pinpoint any message.
| from: | from:[email protected] | Messages from this sender |
| to: | to:team@ | Sent to this address |
| subject: | subject:"quarterly report" | Subject contains phrase |
| body: | body:invoice | Full-text body search |
| has:attachment | has:attachment | Messages with attachments |
| label: | label:Important | Gmail label |
| date: | date:2024-03 | From a given month |
| size:> | size:>5mb | Larger than a size |
| - | -spam | Exclude a term |
| OR | from:alice OR from:bob | Either condition |
Available in 18 languages
Mbox Viewer's interface and user guide are localized into 18 languages, so you can work through your email in the one you know best.
- English
- Español
- Deutsch
- Français
- Italiano
- 日本語
- 한국어
- Nederlands
- Polski
- Português (BR)
- Português (PT)
- Русский
- Svenska
- Dansk
- Norsk
- Türkçe
- 简体中文
- 繁體中文
Free vs Pro, line by line
Same app, same interface, same 18 languages. Pro is not a different program: it is these four things.
| What you can do | Free | Pro |
|---|---|---|
| Maximum mailbox size | 1 GB | Unlimited |
| Search, Gmail labels and conversation threads | Included | Included |
| Export to EML, CSV, plain text and MBOX | Included | Included |
| Extract attachments in bulk | Included | Included |
| Properties, MIME tree and hex views | Included | Included |
| Export to PDF and HTML | One message | In batches |
| Merge mailboxes with deduplication | Up to 1 GB combined | Unlimited |
| Repair damaged mailboxes | Not included | Included |
Pro is a one-time in-app purchase on the Mac App Store or the Microsoft Store — no subscription, no account, no licence key. The price is the one your store shows for your country.