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Transactional Email 1 alternatives tracked

Open-source alternatives to Mailgun

Mailgun is a transactional email API for developers, providing reliable SMTP and REST API delivery for application-generated emails (password resets, order confirmations, notifications). It handles bounce processing, unsubscribe management, and delivery analytics. The free tier includes limited monthly sends; paid tiers scale with volume.

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The alternatives

postal

★ 16,490 Ruby MIT

📮 A fully featured open source mail delivery platform for incoming & outgoing e-mail

postalhq/postal Updated 2026-05-04

Comparison notes

Postal is a full-featured OSS self-hosted mail delivery platform covering SMTP, API sending, bounce handling, and delivery tracking. It is the most direct OSS replacement for Mailgun's server-side sending role. The main gap: Mailgun manages IP reputation, deliverability monitoring, and ISP relationships as part of its SaaS pricing — self-hosted Postal requires managing your own sending IP reputation, SPF/DKIM/DMARC configuration, and ISP relationship (including getting listed on whitelists). For high-volume sending, IP warmup and reputation management are significant operational responsibilities.

Migration tips

  • Export your Mailgun domain configurations (sending domains, webhooks, suppression lists) via the Mailgun API or dashboard
  • Set up Postal on a VPS and configure SPF, DKIM, and DMARC records for your sending domains
  • Import your Mailgun suppression list (bounces, unsubscribes) into Postal before sending — this prevents re-emailing opted-out addresses
  • Update your application's SMTP settings or API endpoint from Mailgun to Postal's API
  • Warm up the new IP gradually (start with low volume, increase weekly) — Mailgun's reputation does not transfer to your new IP

FAQ

Can I fully replace Mailgun with an OSS tool?

Feature parity varies. Most OSS alternatives cover 70-90% of core workflows, but may lack polish, integrations, or specialized features. Pilot the alternative with a subset of your team before fully committing.

What's the cost of self-hosting?

Plan for ~$5-50/month in VPS costs (DigitalOcean, Hetzner, etc.) plus 2-8 hours/month in maintenance. For a team of 20+, self-hosting usually breaks even against SaaS pricing within 6-12 months.

Which alternative should I pick?

Sort by GitHub stars (a proxy for community health), check the last-pushed date (avoid unmaintained projects), and read recent issues to gauge responsiveness.