Introduction

What is Optail?

Optail is an open-source email provider abstraction platform. It sits between your application and your email providers (SendGrid, Postmark, Mailgun, Amazon SES), giving you a single API to send transactional email regardless of which provider is delivering it.

Instead of coupling your application to a single email provider’s API, Optail lets you connect multiple providers, define routing rules, and switch between them instantly — without changing a line of application code. Your templates, unsubscribe lists, and delivery metrics live in Optail, not locked inside a provider’s dashboard.

Optail also gives you platform-level control over things that are typically fragmented across providers: email templates with MJML rendering, unsubscribe group management with HMAC-signed links, unified event tracking (delivered, opened, clicked, bounced), and time-series analytics across all providers.

Key Features

• Provider abstraction — Connect SendGrid, Postmark, Mailgun, and Amazon SES behind a single REST API. Route emails by domain, tags, or priority rules.
• Template engine — Author templates in MJML with Handlebars variables. Version templates, preview with sample data, and roll back to any previous version.
• Unsubscribe management — Create unsubscribe groups, generate HMAC-signed unsubscribe links, and enforce suppressions across provider switches. Suppression state lives in Optail, not your provider.
• Unified metrics — Time-series delivery metrics (sent, delivered, opened, clicked, bounced, complained) with breakdowns by provider, domain, and template.
• Webhook normalization — Receive delivery events from all providers in a single, consistent webhook format.

Architecture

┌─────────────┐      ┌───────────────────────────────────────────────┐
│ Your App    │─────▶│                 Optail API                │
│ (SDK/HTTP)  │      │  ┌──────────┐ ┌──────────┐ ┌──────────────┐  │
└─────────────┘      │  │ Routing  │ │Templates │ │ Suppressions │  │
                     │  │ Engine   │ │ (MJML)   │ │ & Unsubs     │  │
                     │  └────┬─────┘ └──────────┘ └──────────────┘  │
                     │       │                                       │
                     │  ┌────▼─────────────────────────────────┐     │
                     │  │          Provider Adapters            │     │
                     │  │  SendGrid  Postmark  Mailgun  SES    │     │
                     │  └──────────────────────────────────────┘     │
                     └───────────────────────────────────────────────┘
                                         │
                     ┌───────────────────────────────────────────────┐
                     │           Webhook Ingester                    │
                     │  Normalizes provider events into unified      │
                     │  format, stores in TimescaleDB for metrics    │
                     └───────────────────────────────────────────────┘

Tech Stack

Component	Technology
API	Hono on Bun
Database	PostgreSQL 16 + TimescaleDB
Queue	Valkey (Redis-compatible) + BullMQ
Frontend	React 19 + Vite + TanStack Router
Auth	Better Auth
Monorepo	Turborepo with Bun workspaces