
mboxShell. Fast terminal viewer for MBOX files of any size. Open, search and export emails from Gmail Takeout backups (50GB+) without loading them into memory. Built in Rust.
Fast terminal viewer for MBOX files of any size. Open, search and export emails from Gmail Takeout backups (50 GB+) without loading them into memory.
When you export your email from Gmail using Google Takeout, you get one or more .mbox files that can weigh tens of gigabytes — plus one more mailbox per Google Group you own, which is easy to miss and can be larger than the Gmail export itself. There is no cross-platform terminal tool that lets you open, search and browse those files efficiently without loading them entirely into memory.
mboxShell was built to solve that problem: open a 50 GB MBOX in seconds, navigate hundreds of thousands of messages smoothly, search by sender, date or content, and export whatever you need. All from the terminal, with no GUI, no server, no external dependencies.
If you prefer a native graphical experience on macOS, check out mboxViewer — a native Mac app built by the same team. It provides a familiar mailbox-style interface to open, browse and search MBOX files without ever importing them into a mail client. Drag and drop your .mbox file, and you get instant access to all your messages, attachments and labels in a clean macOS-native window. Ideal for users who want the power of mboxShell's parsing engine with the comfort of a desktop GUI.
Need to peek at an MBOX file without installing anything? Try Online Mbox Viewer — a free, MIT-licensed web app by the same author. It opens and renders .mbox files entirely in your browser: nothing is uploaded to any server, so your email stays on your machine. Perfect for a quick look from any device. Source code at github.com/dcarrero/online-mbox-viewer.
.mboxshell.idx) so subsequent opens take less than a second.X-Gmail-Labels as virtual folders in a sidebar panel, letting you filter by Inbox, Sent, Starred, custom labels, etc.topics.mbox files a Takeout archive ships for every group you own, names them after the group instead of the meaningless file name, shows the group as a virtual label, and threads conversations by the exact X-GM-THRID id.encoding_rs.from:, subject:, date:, body:, , , etc.), date ranges, size filters, AND/OR operators, and negation.Download the latest release for your platform from the Releases page:
After downloading, make it executable and move it to your PATH:
# Linux / macOS
chmod +x mboxshell-*
sudo mv mboxshell-* /usr/local/bin/mboxshell
# Or place it in a user-local directory
mv mboxshell-* ~/.local/bin/mboxshell
On Windows, move mboxshell-windows-x86_64.exe to a folder in your PATH, or run it directly.
Requirements: Rust 1.85 or later.
# Clone and build
git clone https://github.com/dcarrero/mboxshell.git
cd mboxshell
cargo build --release
# The binary is at target/release/mboxshell
# Install it system-wide:
sudo cp target/release/mboxshell /usr/local/bin/
# Or for the current user only:
cp target/release/mboxshell ~/.local/bin/
# Add the target you need
rustup target add aarch64-apple-darwin # macOS Apple Silicon
rustup target add x86_64-unknown-linux-gnu # Linux x86_64
rustup target add aarch64-unknown-linux-gnu # Linux ARM64
# Build for a specific target
cargo build --release --target aarch64-apple-darwin
cargo install --git https://github.com/dcarrero/mboxshell.git
# Open an MBOX file in the terminal UI
mboxshell mail.mbox
# Index and show statistics
mboxshell index mail.mbox
mboxshell stats mail.mbox
# Search from the command line
mboxshell search mail.mbox "from:[email protected] date:2024"
mboxshell search mail.mbox "has:attachment subject:invoice" --json
# Export messages
mboxshell export mail.mbox --format eml --output ./emails/
mboxshell export mail.mbox --format csv --output summary.csv
# Extract attachments
mboxshell attachments mail.mbox --output ./attachments/
# Merge multiple MBOX files (duplicates are removed by default)
mboxshell merge file1.mbox file2.mbox -o merged.mbox
# Merge tagging every message with the mailbox it came from
mboxshell merge Inbox.mbox Sent.mbox -o merged.mbox --source-header
# Generate shell completions
mboxshell completions bash > /etc/bash_completion.d/mboxshell
mboxshell completions zsh > ~/.zfunc/_mboxshell
mboxshell completions fish > ~/.config/fish/completions/mboxshell.fish
Global flags:
Merge flags:
| Flag | Description |
|---|---|
--no-dedup | Skip duplicate-Message-ID detection and concatenate the inputs byte-for-byte (dedup is on by default) |
--source-header | Inject an X-Mbox-Source: <mailbox name> header into every message, so a merged archive stays traceable to the mailbox each email came from |
The source label is the mailbox name you see: for an Apple Mail export — a directory Inbox.mbox containing a file literally called mbox — it reads Inbox.mbox, not mbox. Mailboxes that would end up sharing a label are disambiguated against each other (Work/Inbox.mbox vs Personal/Inbox.mbox).

from:[email protected] Search by sender
to:[email protected] Search by recipient
cc:[email protected] Search by Cc recipient
subject:invoice Search in subject line
body:important text Search in message body (full-text)
filename:report.pdf Search by attachment file name
id:<message-id@domain> Search by Message-ID
has:attachment Only messages with attachments
has:no-attachment Only messages without attachments
label:Inbox Filter by Gmail label
date:2024-01 Messages from January 2024
date:2024-01-01..2024-06-30 Date range
before:2024-06-01 Before a date (that day excluded)
after:2024-01-01 From a date on (that day included)
after:2024-01-01 before:2025-01-01 All of 2024
size:>1mb Messages larger than 1 MB
size:>1mb size:<5mb Between 1 and 5 MB
-subject:spam Exclude messages with "spam" in subject
"exact phrase" Search for an exact phrase
from:john subject:budget Implicit AND (both must match)
term1 OR term2 Explicit OR
from:a OR from:b subject:budget OR binds tighter: (a OR b) AND subject
Tested with real Google Takeout MBOX files:
Message list navigation is instantaneous thanks to virtual scrolling (only visible rows are rendered).
The configuration file is located at ~/.config/mboxshell/config.toml:
[general]
default_sort = "date"
sort_order = "desc"
date_format = "%Y-%m-%d %H:%M"
log_level = "warn"
[display]
theme = "dark"
layout = "horizontal"
show_sidebar = false
max_cached_messages = 50
[export]
default_format = "eml"
csv_separator = ","
src/
+-- main.rs # CLI with clap
+-- lib.rs # Module re-exports
+-- error.rs # Error types with thiserror
+-- config.rs # TOML configuration
+-- mailbox_naming.rs # Human-facing mailbox names (Apple Mail packages)
+-- i18n/ # Internationalization (EN/ES)
+-- parser/
| +-- mbox.rs # Streaming parser (never loads the file into memory)
| +-- eml.rs # Individual EML file parser
| +-- mime.rs # MIME decoding, multipart, charsets
| +-- header.rs # RFC 5322 headers, RFC 2047 encoded-words
+-- index/
| +-- builder.rs # Binary index construction
| +-- reader.rs # Index queries
| +-- format.rs # Binary format with SHA-256 integrity check
+-- model/
| +-- mail.rs # MailEntry, MailBody
| +-- attachment.rs # Attachment metadata
| +-- address.rs # RFC 5322 address parsing
+-- store/
| +-- reader.rs # Offset-based reading with LRU cache
+-- search/
| +-- query.rs # Search query parser
| +-- metadata.rs # Fast index search (O(n), < 200ms for 1M messages)
| +-- fulltext.rs # Streaming full-text search
+-- export/
| +-- eml.rs # Export to .eml
| +-- csv.rs # Export summary to CSV (UTF-8 BOM)
| +-- text.rs # Export to plain text
| +-- attachment.rs # Attachment extraction
| +-- mbox.rs # MBOX merge with deduplication and source header
+-- tui/
+-- app.rs # Global state (Elm Architecture)
+-- event.rs # Keyboard event handling
+-- ui.rs # Layout and render dispatch
+-- threading.rs # JWZ algorithm for conversation threads
+-- theme.rs # Color theme
+-- widgets/ # Visual components
+-- mail_list.rs # List with virtual scrolling
+-- mail_view.rs # Message viewer with scroll
+-- sidebar.rs # Labels/folders panel
+-- header_bar.rs # Top bar
+-- status_bar.rs # Status bar
+-- search_bar.rs # Search bar
+-- search_popup.rs # Search filter popup
+-- help_popup.rs # Help popup
+-- attachment_popup.rs # Attachment popup
+-- export_popup.rs # Export popup
mboxshell is developed in the open and is supported by:
If your company finds mboxshell useful and wants to support its continued development, see .github/FUNDING.yml or reach out via carrero.es.
The full user manual covers every command, keyboard shortcut, search operator, export option and config key:
See CHANGELOG.md for the full release history.
MIT - Copyright (c) 2026 David Carrero Fernandez-Baillo - https://carrero.es
Source Code: https://github.com/dcarrero/mboxshell
has:attachmentlabel:| Platform | Binary |
|---|
| Linux x86_64 | mboxshell-linux-x86_64 |
| Linux ARM64 | mboxshell-linux-aarch64 |
| Linux RISC-V 64 | mboxshell-linux-riscv64 |
| FreeBSD x86_64 | mboxshell-freebsd-x86_64 |
| macOS Intel | mboxshell-macos-x86_64 |
| macOS Apple Silicon | mboxshell-macos-aarch64 |
| Windows x86_64 | mboxshell-windows-x86_64.exe |
| Windows ARM64 | mboxshell-windows-arm64.exe |
| Command | Description |
|---|
mboxshell [FILE] | Open a file in the TUI (default action) |
mboxshell open <path> | Open an MBOX file in the TUI |
mboxshell index <path> [-f/--force] | Build or rebuild the binary index |
mboxshell stats <path> [--json] | Show statistics about an MBOX file |
mboxshell search <path> <query> [--json] | Search messages from the command line |
mboxshell export <path> -f <format> -o <output> [--query <q>] | Export messages (formats: eml, csv, txt, html) |
mboxshell merge <files...> -o <output> [--no-dedup] [--source-header] | Merge multiple MBOX files into one |
mboxshell attachments <path> -o <output> | Extract all attachments |
mboxshell completions <shell> | Generate shell completions (bash, zsh, fish, powershell, elvish) |
mboxshell manpage | Generate a man page |
| Flag | Description |
|---|
-f, --force | Force rebuild index even if one exists (in export, -f is --format — spell out --force there) |
-v, --verbose | Increase log verbosity (-v info, -vv debug, -vvv trace) |
--lang <en|es> | Force interface language (auto-detected by default) |
| Key | Action |
|---|
j / k | Next / previous message |
g / G | First / last message |
PgDn / PgUp | Page down / up |
Enter | Open message / switch to message view |
Shift-↑ / Shift-↓ | Scroll selected message body (keeps list focus); a position indicator (Top / NN% / Bot) shows in the message border |
Tab / Shift-Tab | Cycle panel focus |
Esc | Back to list / close popup |
/ | Open search bar |
f | Open search filter popup |
n / N | Next / previous search result |
Space | Mark / unmark message |
* | Mark / unmark all |
s | Cycle sort column (Date, From, Subject, Size) |
S | Toggle sort direction |
e | Export message (EML, TXT, CSV, Attachments) |
a | Show attachments (j/k to navigate, Enter to save, A to save all) |
t | Toggle threaded (conversation) view |
l | Show / focus / hide labels sidebar |
h | Toggle full headers |
r | Toggle raw message source |
1 / 2 / 3 | Layout: list only / horizontal split / vertical split |
? | Help |
q | Quit |
| Format | Extension | Description |
|---|
| MBOX (mboxrd/mboxo) | .mbox | Standard format. Google Takeout, Thunderbird, Unix servers |
| Google Groups export | topics.mbox | Inside a Takeout archive, at <group>@googlegroups.com/. The file name is localised (temas.mbox, …), so the mailbox is named after the group — see docs/GOOGLE-GROUPS.md |
| Apple Mail package | Name.mbox/mbox | The inner file is what gets read; the mailbox is named after the package |
| File size | Messages | Indexing | Re-open |
|---|
| 500 MB | ~5,000 | ~3 s | < 1 s |
| 5 GB | ~50,000 | ~30 s | < 1 s |
| 50 GB | ~500,000 | ~5 min | < 1 s |
| Crate | Purpose |
|---|
ratatui + crossterm | Terminal UI |
mail-parser | MIME/RFC 5322 parsing |
encoding_rs | Charset decoding |
chrono | Dates and time zones |
clap | CLI argument parsing |
serde + bincode | Index serialization |
sha2 | Index integrity verification |
lru | Decoded message cache |
tracing | Structured logging |