The best open source alternative to Mailgun is Postal. If that doesn't suit you, our users have ranked more than 50 alternatives to Mailgun and four of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Mailgun are Mailwhale, Cuttlefish.io and Notifuse.
The open source mail server - Postal is a complete and fully featured mail server for use by websites & web servers. Think Sendgrid, Mailgun or Postmark but open source and ready for you to run on your own servers.
Cuttlefish offers basic bounce email handling, ensuring you maintain your good mail reputation by not resending to bounced addresses.
Modern, self-hosted emailing platform that allows you to send newsletters and transactional emails at a fraction of the cost. Built with Go and React, it provides enterprise-grade features with the flexibility of open-source software.
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