Provide override.conf.sample as a template for customizing systemd
environment paths.
Changes:
- Rename override.conf to override.conf.sample with placeholders and comments
- Update README to instruct copying the sample
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
