EmailEngine vs Hyvor Relay
EmailEngine
emailengine.app
Hyvor Relay
relay.hyvor.comSide by side
| Figure | EmailEngine | Hyvor Relay |
|---|---|---|
| Price from | $120.83/mo | €30/mo |
| Free plan | — | Yes |
| Free trial | Yes | — |
| Open source | — | — |
| Web | Yes | Yes |
| Windows | Yes | — |
| macOS | Yes | — |
| Linux | Yes | — |
| API | Yes | Yes |
| Self-hosted | Yes | Yes |
| Plans published | 2 | 3 |
| Spec score · Email APIs | 8.6 (#4) | 8.6 (#5) |
| Authentication | It offers managed OAuth2, Google Workspace service accounts, Microsoft 365 app-only access, and shared or delegated mailbox support. | Relay requires OpenID Connect (OIDC) for authentication and does not include its own login or signup system. |
| Headquarters | Tallinn, Estonia | Paris, France |
| Product | EmailEngine is a self-hosted email API that connects existing Gmail, Microsoft 365 and IMAP mailboxes through a unified REST API. | Hyvor Relay is an open-source, self-hostable email API designed for developers. |
| Security | Stored mailbox credentials and OAuth2 tokens can be encrypted with AES-256-GCM when the deployment’s EENGINE_SECRET key is configured. | The hosting documentation says its HTTP server has built-in application-layer rate limiting and recommends cloud-provider DDoS protection for network-layer attacks. |
Plans
EmailEngine
- Annual subscription$1,450 a year
- Enterprise perpetual licencePriced on request
Hyvor Relay
- Enterprise License€10,000 a year
- Cloud Standard€30 a month
- Self-Hosted Open-SourceFree
In their own words
EmailEngine
EmailEngine is a self-hosted email API that connects Gmail, Microsoft 365, and IMAP mailboxes through a unified REST API. It sends webhooks when mailbox messages or state change, and can send mail through the connected account’s SMTP server or provider API. Native integrations use the Gmail API and Microsoft Graph; authentication options include managed OAuth2, service accounts for Google Workspace, Microsoft 365 app-only access, and shared or delegated mailboxes. An optional MCP server, currently in beta, lets connected AI clients search, read, file, draft, and send email with approved access. The admin interface shows sync status and queue details, with a Prometheus endpoint and Grafana dashboard for operations. EmailEngine runs on the customer’s infrastructure, uses Redis for sync metadata, and fetches message bodies on demand rather than storing them. A server and Redis using the noeviction policy are required. The annual subscription is $1,450 a year, excluding VAT where applicable, and includes developer support; each installation can start a full-functionality 14-day trial without signup or a credit card.
Hyvor Relay
Hyvor Relay has no write-up on Specifiction yet; its figures are above.