Hyvor Relay

Hyvor Relay is an open-source, self-hosted web app and server that provides a dedicated email API that allows developers to send emails using their own infrastructure via SMTP. By moving the delivery layer to a self-managed environment, users maintain full control over their sending reputation and data privacy.

The software is deployed as a server application using Docker Compose or Docker Swarm. It is designed for developers and organizations that need to manage their own email delivery pipeline, ranging from small projects to high-volume operations sending millions of daily emails. The system includes a dashboard for administrators and a console for users to monitor delivery status.

Key features

• Email API for sending messages via a simple interface
• Multi-tenancy support with scoped access for organizations
• Separate queues for transactional and distributional emails
• Automatic handling of greylisting, retries, and bounces
• Built-in DNS server to automate DNS record management
• Webhooks for receiving HTTP callbacks on email events
• Email suppression management for unsubscribes and bounces
• Monitoring via Prometheus metrics and Grafana dashboards
• Send logs and SMTP conversation history stored for 30 days

The architecture utilizes a PHP and Symfony backend for the API, while Go is used for the email workers, webhook handlers, DNS server, and incoming SMTP server. The frontend is built with SvelteKit and the Hyvor Design System. PostgreSQL serves as both the primary database and the queue system. This distributed approach allows the system to scale horizontally by adding more servers and IP addresses as volume increases. The inclusion of feedback loop integration helps operators manage spam complaints and maintain sender reputation.

Hyvor Relay is licensed under AGPL-3.0 and is a developer-centric tool for high-volume email delivery and infrastructure management.