Overview
Postal is a fully featured open-source mail delivery platform for sending and receiving large volumes of transactional and bulk email. It provides a web UI, HTTP API, SMTP relay, message tracking, webhooks, and per-domain DKIM. Written in Ruby, it is designed as a self-hosted alternative to SendGrid, Mailgun, and Postmark. It is widely used to run your own outbound email infrastructure.
Key features
- Sends and receives transactional and bulk email at high volume
- SMTP relay plus an HTTP API for integrating with applications
- Web UI for managing domains, queues, and message flow
- Message tracking with delivery, open, and click events
- Per-domain DKIM signing
- Webhooks for delivery and event notifications
Our take
Postal is a full mail delivery platform rather than a thin SMTP wrapper, covering sending, receiving, tracking, webhooks, and per-domain DKIM, which makes it a credible self-hosted stand-in for SendGrid or Mailgun. The honest caveat is that running your own mail server is the hard part, not the software: IP warming, reverse DNS, SPF/DKIM/DMARC alignment, and staying off blocklists are ongoing operational work that a managed provider otherwise absorbs for you. That's reflected in the higher setup difficulty and the fact that it's self-host only with no hosted offering. The MIT license is permissive and the Ruby codebase is mature and widely deployed. If deliverability ownership is the goal and you have the ops appetite, Postal is a solid foundation; if you just want emails to arrive with minimal fuss, a hosted API is less stressful.
Ideal for: Teams with sysadmin experience who want to own their outbound email infrastructure instead of paying per-email to a provider.
Where it falls short of SendGrid
- You are responsible for IP reputation, warmup, and deliverability
- Requires MariaDB, RabbitMQ, and DNS/DKIM configuration to run
- No marketing-campaign UI — it is a delivery engine, not a newsletter builder
- Less hand-holding than managed providers for spam/blocklist issues
We list the gaps honestly so you can decide if the trade-off is worth owning your data.
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