Posta

Posta is a self-hosted email delivery platform that allows applications to send emails through HTTP APIs while Posta manages SMTP delivery, templates, storage, security, and analytics.

It provides a developer-friendly and fully self-hostable alternative to services such as SendGrid, and Mailgun.

Send Your First Email

Example request:

curl -X POST http://localhost:9000/api/v1/emails/send \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "hello@example.com",
    "to": ["user@example.com"],
    "subject": "Hello from Posta",
    "html": "<h1>Hello!</h1>"
  }'

Response:

{
  "id": "email_01J8C8E5W3",
  "status": "queued"
}

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Features

Email Delivery

• HTTP Email API Send single, batch, or template-based emails via REST endpoints.

• File Attachments Attach files to emails using base64-encoded content.

• Custom Headers & Unsubscribe Set custom email headers and automatic List-Unsubscribe support (URL and POST-based).

• Scheduled Delivery Queue emails for delivery at a specified time.

• Email Preview Render and preview emails without sending via the API or dashboard.

• Email Status Polling Lightweight status endpoint for tracking delivery state of individual emails.

• Asynchronous Processing Background workers process email queues using Redis and Asynq with priority tiers (transactional, bulk, and low-priority).

• Automatic Retry Failed emails are retried automatically with configurable retry limits per SMTP server. Retry failed emails manually from the dashboard.

• Development Mode Store and preview emails in the dashboard without sending them.

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Templates

• Versioned Templates Create multiple template versions with a selectable active version.

• Multi-language Support Templates support language-specific versions with variable substitution.

• Managed Stylesheets Stylesheets are automatically inlined for email client compatibility.

• Template Preview Render and preview templates directly from the dashboard.

• Template Import / Export Export templates as JSON and import them across environments.

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SMTP and Domain Management

• Multiple SMTP Servers Configure multiple SMTP servers per user with SSL or STARTTLS support.

• Shared SMTP Pool Administrators can define shared SMTP servers available to all users.

• Domain Verification Verify domain ownership via DNS records including SPF, DKIM, and DMARC.

• Verified Sending Enforcement Optionally restrict sending to verified domains only.

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Security and Authentication

• API Key Authentication Secure API keys with hashing, prefix identification, expiration, IP allowlisting, and revocation.

• Dashboard Authentication JWT-based authentication with role-based access control.

• Two-Factor Authentication TOTP-based 2FA setup and verification.

• Session Management List active sessions, revoke individual sessions, or force-logout all other sessions.

• Rate Limiting Redis-backed hourly and daily email limits per user.

• CORS Support Configurable allowed origins for cross-origin requests.

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Contacts and Suppression

• Contact Management Automatically track recipients with send and failure statistics.

• Contact Lists Organize recipients into reusable mailing lists.

• Bounce Tracking Track hard bounces, soft bounces, and complaints.

• Automatic Suppression Automatically suppress recipients based on bounce behavior.

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Events and Webhooks

• Webhooks Subscribe to events such as email.sent and email.failed with HMAC-SHA256 signature verification.

• Webhook Delivery History Track delivery attempts, HTTP status codes, retry counts, and response details per webhook.

• Configurable Retries Set max retries and request timeout per webhook with exponential backoff.

• Audit Logs Track platform and user activity with filtering and real-time streaming using Server-Sent Events.

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Analytics and Monitoring

• Email Analytics View daily email volume and status breakdown with date filtering.

• Dashboard Statistics Delivery rate trends, bounce rate graphs, and latency percentiles.

• Daily Reports Opt-in daily email reports with sent/failed counts and delivery rate per user.

• Prometheus Metrics Export metrics including request counts, latencies, email delivery counters, and webhook delivery stats.

• Health Probes Liveness (/healthz) and readiness (/readyz) endpoints.

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Admin Panel

• User Management Create, deactivate, and manage users and roles. Disable 2FA for users. View per-user metrics.

• Platform Metrics Aggregate statistics across the entire platform including total users, emails, bounces, and suppressed recipients.

• Shared SMTP Servers Manage SMTP servers available to all users with domain allowlists and strict/permissive security modes.

• API Key Management List and revoke API keys across all users.

• Platform Email Logs View and search emails across all users.

• Job Monitoring Track scheduled cron jobs such as retention cleanup and daily reports with execution history and error tracking.

• Platform Settings Configure registration, retention policies (email logs, audit logs, webhook deliveries), and bounce handling.

• Real-time Event Streaming Live audit log updates via Server-Sent Events.

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Data Management and GDPR

• User Data Export Export all user data (templates, stylesheets, contacts, contact lists, webhooks, suppressions, and settings) as JSON.

• User Data Import Import previously exported data with duplicate handling.

• GDPR Contact Deletion Delete specific contacts or all contacts with associated suppressions and list memberships.

• Email Log Cleanup Delete email logs and associated bounces older than a specified number of days.

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Dashboard

• Vue.js Web Interface Manage templates, SMTP servers, domains, API keys, contacts, webhooks, and email logs.

• Dark and Light Themes Toggle between dark and light mode.

• User Settings Configure timezone, default sender, notification preferences, API key expiration, bounce handling, and daily reports.

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Deployment

• Embedded Worker Mode Run the background worker within the API server process using POSTA_EMBEDDED_WORKER for simpler deployments.

• Configurable Worker Concurrency Tune worker parallelism with POSTA_WORKER_CONCURRENCY.

• Automatic Database Migrations Schema is created and migrated automatically on startup.

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API Documentation

• Swagger UI — /docs
• ReDoc — /redoc

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Tech Stack

Frontend

• Framework: Vue 3 with Composition API
• Build Tool: Vite
• State Management: Pinia
• HTTP Client: Axios

Backend

• Language: Go
• Framework: Okapi
• Database: PostgreSQL
• Queue: Redis with Asynq
• Metrics: Prometheus-compatible

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Requirements

• Go 1.25+
• PostgreSQL
• Redis

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Quick Start

Local Development

git clone https://github.com/jkaninda/posta.git
cd posta

make dev-deps
make dev
make dev-worker

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Docker Compose

docker compose up -d

This starts:

• Posta API server
• Background worker
• PostgreSQL
• Redis

Dashboard:

http://localhost:9000

Default admin credentials:

Email: admin@example.com
Password: admin1234

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Dashboard

Posta includes a web dashboard for managing templates, SMTP servers, domains, contacts, API keys, and analytics.

Email Analytics

Email Logs

Email Detail

Template Detail

Template Preview

Admin Platform Metrics

Admin Metrics (Light)

Admin Metrics (Dark)

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Official Clients

• Go: https://github.com/jkaninda/posta-go
• Php: https://github.com/jkaninda/posta-php
• Java: https://github.com/jkaninda/posta-java

Go Client SDK

An official Go client is available:

Install:

go get github.com/jkaninda/posta-go

Example:

package main

import (
    "fmt"
    "log"

    posta "github.com/jkaninda/posta-go"
)

func main() {
    client := posta.New("https://posta.example.com", "your-api-key")

    resp, err := client.SendEmail(&posta.SendEmailRequest{
        From:    "sender@example.com",
        To:      []string{"recipient@example.com"},
        Subject: "Hello from Posta",
        HTML:    "<h1>Hello!</h1>",
    })

    if err != nil {
        log.Fatal(err)
    }

    fmt.Printf("Email sent: id=%s status=%s\n", resp.ID, resp.Status)
}

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Contributing

Contributions are welcome! Please open an issue to discuss proposed changes before submitting a pull request.

License

Copyright 2026 Jonas Kaninda

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

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Made with ❤️ for the developer community

⭐ Star us on GitHub — it motivates us to keep improving!

Copyright © 2026 Jonas Kaninda