Here's a list of open-source mail servers that you can use to send/receive emails and store mail.

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Postal Postal is a feature-rich mail server that can be utilized by websites and servers. Cuttlefish is a no-nonsense open-source mail server suite with tools that help you build a web server, manage your mailbox, and more. Haraka Haraka is a modern open source SMTP server built with Node.

12 Best Open Source Email Servers

Ready to Build and Manage Your Email Server?

<p><a href="https://www.bennetrichter.de/en/tutorials/mailcow-dockerized/" target="_blank" rel="noopener nofollow">https://www.bennetrichter.de/en/tutorials/mailcow-dockerized/</a>
This is a good tutorial if you want to get started with mailcow</p>
