dead-letter 0.1.1

Convert .eml email exports to Markdown with YAML front matter

dead-letter

Your .eml files deserve a second life.

dead-letter converts email exports into clean Markdown with YAML front matter — threads split, signatures stripped, attachments extracted, calendars parsed. One file or ten thousand.

✨ Features

• Full-fidelity conversion — HTML sanitization, Gmail/Outlook thread segmentation, inline image handling, and calendar event summaries
• CLI — point it at a file or a directory and go
• Local web UI — dark command-center interface with drag-and-drop import, watch mode, conversion grade badges, processing history, and per-job diagnostics
• Inbox/Cabinet workflow — drop .eml files into an Inbox, let dead-letter organize the Markdown bundles into a Cabinet
• Install validation — dead-letter doctor checks your runtime environment
• Conversion report — opt-in JSON report with per-file diagnostics for automation and audit
• Python API — from dead_letter import convert and you're off

🧠 Built for LLM Pipelines

Raw .eml files are noisy input for downstream LLM and retrieval pipelines — MIME headers, multipart boundaries, duplicated HTML/plain bodies, and encoded attachments all get mixed into the text path.

dead-letter normalizes that into Markdown with YAML front matter, so message text and metadata are ready for chunking or indexing without MIME parsing or base64 cleanup. Default convert() and convert_dir() runs write a single .md per message and keep attachment names in front matter.

If you want the filesystem artifacts separated too, bundle and Cabinet workflows write message.md plus decoded files under attachments/. The Markdown is ready for text ingestion, while PDFs, spreadsheets, calendar files, and other binary attachments stay cleanly split out for whatever downstream parser you already use.

📦 Install

pip install dead-letter            # core + CLI
pip install dead-letter[cli]       # + watch mode (watchfiles)
pip install dead-letter[ui]        # + web UI, API server, and watch mode

Or use pipx for an isolated install:

pipx install 'dead-letter[ui]'   # installs dead-letter and dead-letter-ui commands

From source:

git clone https://github.com/BigCactusLabs/dead-letter.git
cd dead-letter
uv sync --extra dev

🚀 Quick Start

CLI — convert a single file:

dead-letter convert message.eml

Convert a whole directory:

dead-letter convert inbox/ --output out/

Generate a JSON conversion report alongside the output:

dead-letter convert inbox/ --output out/ --report

With --output, the report is written to that output directory as .dead-letter-report.json. Without --output, file conversions write the report next to the source message and directory conversions write it to the input directory root.

Check your runtime environment:

dead-letter doctor

Directory conversion scans recursively for .eml files, matches the suffix case-insensitively, and skips symlinked files whose resolved targets escape the requested input tree.

Web UI — start the local server:

dead-letter-ui --host 127.0.0.1 --port 8765

Open http://127.0.0.1:8765 — on first launch, a setup prompt suggests default Inbox and Cabinet folders. Configure or skip to start converting. Import .eml files with drag and drop or the file picker. Single-file imports use file mode, while multi-file drops create one directory-mode batch job. Mixed drops ask for confirmation before skipping non-.eml files.

From a source checkout, prefix with uv run:

uv run dead-letter convert message.eml
uv run dead-letter-ui --host 127.0.0.1 --port 8765

🐍 Python API

from dead_letter import convert

result = convert("message.eml")
print(result.subject, result.sender)
print(result.output)  # path to the generated .md

With options:

from dead_letter import convert, ConvertOptions

result = convert("message.eml", options=ConvertOptions(
    strip_signatures=True,
    strip_quoted_headers=True,
))

Strip signature images (logos, social icons) and tracking pixels:

result = convert("message.eml", options=ConvertOptions(
    strip_signature_images=True,
    strip_tracking_pixels=True,
))

Bundle conversion (Markdown + attachments + source in one directory):

from dead_letter import convert_to_bundle

bundle = convert_to_bundle("message.eml", bundle_root="cabinet/")
print(bundle.markdown)     # cabinet/message/message.md
print(bundle.attachments)  # [cabinet/message/attachments/logo.png, ...]

Extracted attachment filenames are normalized to safe basenames before they are written under attachments/.

Batch:

from dead_letter import convert_dir

for r in convert_dir("inbox/", output="out/"):
    print(f"{'✓' if r.success else '✗'} {r.source.name}")

🗂 Project Structure

src/dead_letter/
├── core/           # conversion pipeline (MIME, HTML, threads, rendering)
├── backend/        # CLI, API server, job runner, watch mode
└── frontend/       # static web UI (htmx + Alpine.js)
tests/
├── core/           # conversion pipeline tests with .eml fixtures
├── backend/        # API, job, and watch tests
└── frontend/       # JS unit tests

🧪 Testing

uv run pytest tests/core           # conversion pipeline
uv run pytest tests/backend        # API and job runner
node --test tests/frontend/*.test.js     # frontend

CI runs all three on every push and PR.

📚 Docs

• Docs Index — public docs landing page
• Runtime Contracts — full API and core behavior spec
• Frontend State Model
• Quality Diagnostics
• Brand & Style Guide
• Changelog
• Contributing

⚠️ Known Limitations (v0.1)

• Local-only — no remote server, no auth
• In-memory job registry (state resets on restart)
• Single-user, single-machine

License

PolyForm Noncommercial 1.0.0 — free for personal, educational, and nonprofit use. Commercial use requires a separate license from Big Cactus Labs.