Implement email forwarder

Add core IMAP forwarding logic with time-based searches and Message-ID
deduplication to prevent duplicates in destination mailbox.

Changes:
- Implement SINCE-based email search using last_run.txt for incremental forwarding
- Add Message-ID extraction and IMAP checks for deduplication
- Configure systemd user services with drop-in overrides for portability
- Integrate Uptime Kuma pings for monitoring
- Set up virtual environment for dependency isolation
- Update documentation and configuration templates

README.md

@@ -0,0 +1,59 @@
+# Email Forwarder
+
+This script forwards new emails from a source IMAP account (e.g., GMX) to a destination IMAP account (e.g., MXRoute), avoiding duplicates by tracking Message-IDs and using time-based searches.
+
+## Setup
+
+1. Copy `.env.example` to `.env` and fill in your IMAP credentials, Uptime URLs, and settings.
+
+2. Create virtual environment: `python -m venv venv`
+
+3. Activate and install: `source venv/bin/activate && pip install -e .`
+
+4. For user services (recommended):
+   - Copy services: `cp *.service *.timer ~/.config/systemd/user/`
+   - Copy drop-in: `cp -r email_forwarder.service.d ~/.config/systemd/user/`
+   - Edit `~/.config/systemd/user/email_forwarder.service.d/override.conf` to set `PROJECT_DIR` to your project path.
+
+5. Reload and enable: `systemctl --user daemon-reload && systemctl --user enable email_forwarder.timer && systemctl --user start email_forwarder.timer`
+
+6. Check status: `systemctl --user status email_forwarder.timer`
+
+## Configuration (.env)
+
+- `SOURCE_HOST`: Source IMAP server (e.g., imap.gmx.com)
+- `SOURCE_PORT`: Port (default 993)
+- `SOURCE_USER`: Source email/username
+- `SOURCE_PASS`: Source password
+- `DEST_HOST`: Destination IMAP server (e.g., yourserver.mxrouting.net)
+- `DEST_PORT`: Port (default 993)
+- `DEST_USER`: Destination email/username
+- `DEST_PASS`: Destination password
+- `FOLDER`: Mailbox folder (default INBOX)
+- `DRY_RUN`: Set to `true` for testing without forwarding (default false)
+- `UPTIME_SUCCESS_URL`: URL for success ping
+- `UPTIME_FAIL_URL`: URL for failure ping
+
+## How It Works
+
+- Uses time-based search (`SINCE`) with `last_run.txt` to find emails since last run.
+- Extracts Message-ID, checks against local file and destination IMAP for duplicates.
+- Forwards via IMAP APPEND; updates `last_run.txt` on success.
+- Logs activity; systemd handles Uptime Kuma pings.
+
+## Monitoring with Uptime Kuma
+
+- Success: Pings `${UPTIME_SUCCESS_URL}` after forwarding.
+- Failure: `OnFailure` pings `${UPTIME_FAIL_URL}`.
+
+## Dependencies
+
+- imaplib, email (built-in)
+- python-dotenv, imap-tools
+- systemd (for user services)
+
+## Troubleshooting
+
+- Logs: `journalctl --user -u email_forwarder.service`
+- Test: `source venv/bin/activate && python main.py`
+- Timezone issues: Adjust UTC offset in script if needed.