Email Spam Tester

I run mail infrastructure for an email service provider as my day job, and the "my emails go to spam" cases I see usually come down to a DNS record or a header nobody looked at. Email Spam Tester is the tool I wanted for that. You copy a disposable address, send it the actual email from the platform that will send the campaign, and the report opens on its own. It runs 42 checks: SPF, DKIM, DMARC and their alignment, ARC, reverse DNS, TLS, 20-odd blocklists, two separate spam engines, HTML, every link followed to its final destination, and the bulk-sender rules Gmail and Yahoo enforce since 2024. Each warning quotes the RFC section it rests on. AI goes through the whole message: every header, both bodies, the sending server, each link and the DNS of every domain involved. It works by the RFCs (5321, 5322, 7208, 6376, 7489, 8058 and the rest), and writes a fix plan with the DNS record to paste for each change. The points next to each fix come from re-scoring the report with that fix applied. On the same send you can add real mailboxes at Gmail, Outlook, Yahoo, GMX, Proton and other providers (14 in total) and see whether the message went to the inbox, a tab or spam at each. Developers get the whole thing as a REST API, no key needed to start: create a test address, poll the status, read the report as JSON. There are also 14 domain-check endpoints (SPF, DMARC, DKIM, MX, BIMI, MTA-STS, DANE, blocklists and more) and an infrastructure check that audits a domain in one call, stores every run and returns a diff against your previous one. For AI agents there is a remote MCP server with four tools and a SKILL.md file. Integrations exist for Mailchimp, HubSpot, Zapier, n8n, WordPress, cPanel, Plesk and ChatGPT. No account, no card. Reports have a permanent link and read in 31 languages.