In simple English
When you send emails, you want to know if they land in the inbox or the spam folder. This tool runs its own mail server and spam filters to grade your outgoing mail. It checks your technical records like SPF, DKIM, and DMARC to spot problems early. You can host it on your own server for free, but you need some technical skill to set up email routing and DNS. It takes ongoing work to keep your mail server secure and unblocked.
What it is
An open-source, self-hosted email deliverability testing platform that analyzes test emails and provides detailed deliverability reports with scoring. It runs a mail server and checks your setup against multiple spam filters and blocklists.
What it is good for
Solo builders who send transactional or marketing emails and want to check if their authentication and content will trigger spam filters before sending to real customers.
- Provides a complete grade from A to F across multiple deliverability factors.
- Includes a full REST API for automated testing in your deployment pipeline.
- Bundles SpamAssassin, rspamd, and Postfix in an all-in-one Docker image.
- Requires managing port 25 and proper DNS records, which can be tricky with cloud providers.
- The bundled Docker image needs around 1.5 GB of memory to run all internal services.
- Uses the AGPL-3.0 licence, which has strict rules if you modify the code and offer it as a service.
Paid email testing services like Mail-tester or GlockApps
Postfix
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git clone https://git.nemunai.re/happyDomain/happyDeliver.git cd happydeliver docker-compose up -d