mailtesterbox
Email deliverability tester
Send one email to a disposable address and get a deliverability score out of 10, with the reason behind every lost point.
- For
- Developers, sysadmins and anyone whose mail lands in spam.
- Platforms
- Web · API
- Links
What it is
mailtesterbox gives you a temporary address. You send a mail to it, and a few seconds later you get a report: SPF evaluated against the sending IP, DKIM signatures verified cryptographically, DMARC policy and alignment, forward-confirmed reverse DNS, HELO, TLS, 27 IP blacklists, 4 domain and URL blacklists, SpamAssassin with the full rule breakdown, and content checks.
The engine is open source. Blacklists refuse queries from public resolvers, so it runs its own unbound resolver that resolves from the root servers; otherwise every check would come back as a false positive.
What it does
- Score out of 10 with per-check explanations
- SPF, DKIM, DMARC, rDNS, HELO, TLS
- 27 IP and 4 domain/URL blacklists
- SpamAssassin rule breakdown
- Content checks: plain-text part, image ALT, short links, unsubscribe link
- Turkish and English UI, accounts and an API
How it’s built
- Mail path
- Analysis
- Infra