With over 15,000 GitHub stars accumulated since its February 2025 launch, BillionMail delivers the rare combination of a production mail transfer agent and a full email marketing suite in a single self-hosted package — eliminating the monthly per-subscriber fees charged by Mailchimp, SendGrid, and similar platforms. The Go-based architecture bundles Postfix for SMTP transmission, Dovecot for IMAP and POP3 mailbox access, Rspamd for intelligent spam filtering and greylisting, and RoundCube for browser-based webmail, all orchestrated through Docker Compose with PostgreSQL for persistent storage and Redis for queue management and caching. The marketing engine supports unlimited subscriber lists with tag-based segmentation, scheduled campaign sends, A/B subject line testing, and both HTML and drag-and-drop visual template editors for crafting responsive emails without coding. Real-time analytics dashboards track sent volume, deliverability rate, open rate, click-through rate, and bounce reasons, while the platform provides step-by-step DNS record configuration wizards for SPF, DKIM, and DMARC to maximize inbox placement. A transactional email API exposes REST endpoints for single and batch sending, enabling integration with CRM systems, e-commerce platforms, and custom applications. Auto-provisioned free SSL certificates, Fail2ban brute-force protection, and privacy-first architecture with zero third-party tracking ensure secure operation. The platform installs in under eight minutes via a single shell script and supports SMTP on port 25, SMTPS on 465, submission on 587, IMAP on 143/993, and POP3 on 110/995. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPLv3 licensed.

Plunk consolidates transactional emails, marketing campaigns, and drip automation into one platform riding AWS SES at roughly one-tenth of a cent per message, with zero per-contact charges regardless of list size. The Turborepo monorepo architecture separates the Express.js API server (handling REST requests with Prisma ORM against PostgreSQL) from a dedicated BullMQ worker process that consumes email, campaign, and workflow jobs independently for fault isolation and horizontal scaling. Transactional emails support HTML bodies, template variable substitution via React Email components, attachments, and custom headers with dedicated SMTP relay on ports 465 and 587 for integration with existing frameworks. The campaign system sends newsletters and product updates to full contact lists or dynamically segmented audiences based on contact properties and behavioral events, with scheduling, A/B testing, and performance tracking for opens, clicks, and bounces. The workflow automation builder creates event-triggered sequences with delays, conditional branches, and webhook steps for lifecycle campaigns like onboarding drip sequences and re-engagement flows. Contact management stores unlimited contacts with custom data fields, CSV import, full activity history, and dynamic segmentation. Custom domain verification with DKIM and SPF ensures deliverability, while inbound email processing handles incoming messages with custom routing rules. Docker Compose deployment runs five containers including PostgreSQL, Redis, MinIO for S3-compatible storage, and ntfy for notifications. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.

Larasend gives Laravel teams a self-hosted transactional email platform that sends through their own Amazon SES or Cloudflare account while keeping the dashboard, delivery logs, and message data on their own servers. Send mail with a simple POST to the emails API, or point existing mailables and notifications at the Larasend transport with one environment variable and no code rewrite. Every message lands in an activity dashboard where you can filter by status, search recipients and message IDs, open a preview with headers and metrics, and resend failures in one click. Delivery, bounce, complaint, open, and click events stream back from the provider and update each message timeline, so a missing receipt becomes a traceable record instead of a support mystery. Suppression lists build themselves from bounces and complaints, and guardrails watch complaint rates and verified domains before reputation damage can spread. Scoped API keys with expiration and rotation keep each project separate, while workspace roles control who can view, send, and administer. When replies arrive, the shared inbox threads inbound and outbound mail into conversations your team can assign, snooze, annotate, and answer with attachments and drafts. Webhooks notify your other systems about deliveries and inbound mail, and reusable templates keep recurring notices consistent across projects. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. MIT licensed.

Built as a developer-first alternative to SendGrid, Mailgun, and Postmark, Posta delivers a complete self-hosted email infrastructure platform handling both outbound delivery and inbound reception through a single HTTP API with official SDKs for Go, PHP, and Java. The Go backend processes email through Redis and Asynq with automatic retries, priority queues, and async delivery while PostgreSQL stores templates, contacts, campaigns, and delivery analytics. Outbound features include versioned multi-language templates with variable substitution and stylesheet inlining, bulk campaigns with subscriber targeting and A/B testing per-variant metrics, scheduled timezone-aware delivery with draft/paused/cancelled lifecycle states, email address verification checking syntax, MX records, disposable domains, and role accounts, plus web view links with signed expiring URLs and one-click unsubscribe headers. The built-in SMTP receiver with TLS handles inbound email at your domains, parses messages and attachments, scores spam, and forwards structured payloads to your application via HMAC-verified webhooks with real-time SSE notification streams. The Vue-based dashboard manages templates, SMTP server pools, domains, contacts, API keys, campaigns, and email logs with dark and light mode support while admin-level platform metrics expose delivery rate trends, bounce rate graphs, and latency percentiles alongside Prometheus integration and daily health reports. Deploy via Docker with PostgreSQL and Redis. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. Apache 2.0 licensed.

MillionSend is an open-source email platform you run yourself that sends transactional and marketing mail through your own AWS SES account behind a Resend-compatible API. Every message you send becomes a row in the dashboard, and every row opens into a timeline of SES events with the raw payload and the SMTP diagnostic when something bounces. Daily metrics chart sent, delivered, opened, clicked, bounced, and complained volumes against SES thresholds, and broadcasts stop on their own at five percent bounces or 0.1 percent complaints before Amazon can pause your account. Contacts live once for the whole team with custom properties and subscribe state, while segments and topics decide exactly who receives each broadcast. You compose broadcasts from reusable templates with per-contact merge fields, schedule them ahead, and cancel them while they wait. Applications that only speak SMTP send through the relay on port 2587 with an API key as the password, and HTTP integrations use idempotency keys, request logs with secrets redacted, and signed webhooks with a delivery history. Guided domain setup handles DKIM records, hard bounces and complaints are suppressed automatically, and every recipient gets an RFC 8058 one-click unsubscribe. Receiving and agent-ready inboxes are included in beta for mail sent to your verified domains. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.