legacy-email-proxy/README.md

# Legacy Email Proxy

Proxy an unauthenticated, unencrypted POP3 / SMTP server to authenticated IMAPS and SMTPS backends.

## Features

- Exposes legacy `POP3` on `0.0.0.0:110` and legacy `SMTP` on `0.0.0.0:25`
- Forwards POP3 mailbox access to an IMAP backend
- Forwards SMTP submissions to an SMTPS backend
- Backend host, ports, and credentials are configured via environment variables

## Environment Variables

- `POP3_BIND_ADDR` (default `0.0.0.0`)
- `POP3_BIND_PORT` (default `110`)
- `SMTP_BIND_ADDR` (default `0.0.0.0`)
- `SMTP_BIND_PORT` (default `25`)

- `BACKEND_IMAP_HOST`
- `BACKEND_IMAP_PORT` (default `993`)
- `BACKEND_IMAP_USER`
- `BACKEND_IMAP_PASS`
- `BACKEND_IMAP_USE_SSL` (default `true`)
- `BACKEND_IMAP_USE_STARTTLS` (default `false`)

- `BACKEND_SMTP_HOST`
- `BACKEND_SMTP_PORT` (default `465`)
- `BACKEND_SMTP_USER`
- `BACKEND_SMTP_PASS`
- `BACKEND_SMTP_USE_SSL` (default `true`)
- `BACKEND_SMTP_USE_TLS` (default `false`)

## Build and run

This project targets the latest Python LTS release. The included `Dockerfile` uses `python:3.12-slim`, which is compatible with Python 3.12 and later LTS releases.

```bash
docker build -t legacy-email-proxy .
docker run --rm -p 110:110 -p 25:25 \
  -e BACKEND_IMAP_HOST=imap.example.com \
  -e BACKEND_IMAP_PORT=993 \
  -e BACKEND_IMAP_USER=imap-user \
  -e BACKEND_IMAP_PASS=imap-pass \
  -e BACKEND_SMTP_HOST=smtp.example.com \
  -e BACKEND_SMTP_PORT=465 \
  -e BACKEND_SMTP_USER=smtp-user \
  -e BACKEND_SMTP_PASS=smtp-pass \
  legacy-email-proxy
```

## Tests

Install development dependencies and run the test suite:

```bash
python -m venv .venv
source .venv/bin/activate
python -m pip install --upgrade pip
pip install -r requirements-dev.txt
pytest -q
```

## Notes

This implementation begins the proxy with a minimal POP3 command set and SMTP delivery path. It is designed to start development on the required application architecture.