Open-source Amazon SES alternatives

Postal is a complete mail server for websites and web servers that handles both outgoing and incoming email. The project describes it as an open-source take on services such as Sendgrid, Mailgun and Postmark, ready to run on your own servers rather than rented as a hosted API.

It is written in Ruby and released under the MIT license. The project provides documentation with installation instructions, an FAQ and features list, a separate repository of installation tools, and community support through GitHub Discussions and Discord. Repository topics list Ruby, mail, SMTP and mail server.

Because it is self-hosted, Postal suits teams that want control over their own email delivery infrastructure instead of relying on a hosted provider, such as websites that send transactional messages.

Plunk is an open-source email platform that combines transactional email, marketing campaigns and workflow automation in a single product. Developers can send messages from an API with templates and variable substitution, or use Plunk as an SMTP relay so that existing tools and frameworks can send through it.

Marketing features include campaigns for newsletters and product updates, dynamic segments, and contact management with custom fields and activity history. Workflows add triggers, delays and conditional logic, analytics track opens, clicks and bounces, custom domains are verified with DKIM and SPF, and inbound emails can be received and routed with custom rules.

Plunk is positioned as an open-source, self-hosted alternative to services such as SendGrid, Resend and Mailgun. It is licensed under AGPL-3.0, written in TypeScript, and can be deployed from an official Docker image following the project's documentation. The README cites a rate of $0.001 per email with no contact limits.