relay vs e2a
Email APIs for self-managed infrastructure and agent workflows
relay and e2a both provide APIs for working with email, with options to run the infrastructure yourself. relay focuses on managing outbound delivery through your own SMTP infrastructure, while e2a combines sending with inbound mailboxes and workflows for applications and AI agents.
relay: Send Email Through Your Own SMTP Infrastructure
Hyvor Relay is a self-hosted email API that sends and manages email through your own SMTP infrastructure. It suits teams that want delivery controls, logs, and multi-tenant project management without relying on a hosted email API.
e2a: Email API for Applications and AI Agents
e2a provides an email API and relay for applications and AI agents. It supports transactional sending, inbound mailboxes, and agent replies, with optional human review and hosted or Docker-based deployment.
| relay | e2a | |
|---|---|---|
| Language | PHP | Go |
| License | AGPL-3.0 | Apache-2.0 |
| Stars | 918 | 192 |
| Forks | 65 | 26 |
| Last analyzed | Oct 12, 2026 | Oct 4, 2026 |
Key differences
- relay is centered on outbound email delivery, including separate transactional and distributional queues; e2a handles both outbound sending and inbound mail.
- relay provides tenant and project management, delivery logs, and SMTP monitoring; e2a offers inbound access through polling, WebSockets, webhooks, and MCP tools.
- relay combines PHP and Symfony, Go services, and a SvelteKit frontend; e2a is Go-based.
- relay is licensed under AGPL-3.0; e2a is licensed under Apache-2.0.
- relay supports Docker Compose or Swarm and uses PostgreSQL for its database and queues; e2a supports Docker with PostgreSQL or a hosted service.
- relay is described as actively maintained with regular commits and releases; e2a documents some beta capabilities, including templates and parts of its review and protection APIs.
Choose relay if you…
- need to operate SMTP infrastructure while managing delivery through an API.
- want separate tenants and projects, delivery logs, and visibility into SMTP conversations.
- send both transactional and distributional email and want separate queues with automated retry and bounce handling.
Choose e2a if you…
- need applications or AI agents to receive email and reply in-thread.
- want inbound email access through polling, WebSockets, webhooks, or MCP tools.
- prefer an Apache-2.0 project or want the option to start with a hosted service.
Compare the numbers side by side, or add more projects
This comparison is generated with AI from the OSRepos analyses of both projects. Always check each project's repository and documentation before choosing.