Show HN: E2a – Open-source email gateway for AI agents

We were building an agent system and wanted email as a trigger. We decided to take it out and made it a standalone service.

The primary email features we wanted and used for our own agent system:

1. Email threading stays consistent with agent conversation threading

2. Human in the loop review for outbound emails (especially during testing phase)

3. Quick onboarding/offboarding email addresses for agents within minutes

4. Websocket for local agents and at-least-once webhook delivery