About
Why we built this
Testing email deliverability is often a frustrating cycle. Most diagnostics tools share a major limitation: they only allow one email per generated address.
Comparing how Google Workspace, Microsoft 365, and your transactional SMTP provider authenticate means generating separate addresses, sending separate emails, and juggling multiple browser tabs.
The Solution
One address. Multiple emails. Full clarity.
Test One Mail gives you one address to send multiple emails to. All diagnostics are grouped side-by-side via real-time WebSockets — compare providers, detect alignment issues, and resolve deliverability problems from a single view.
Core Capabilities
- Side-by-Side Comparison — Compare SPF, DKIM, and DMARC alignment from different sources on one page.
- Real-Time Stream — WebSocket push notifications update reports instantly as emails arrive.
- Standards-Compliant Checks — Real verification of SPF records, DKIM signatures, and DMARC policy alignment.
- Blocklist Screening — Checks sending IPs against 23 common DNS-based blocklists including Spamhaus, Barracuda, and SPAMCOP.
- Shareable Links — Copy a unique report URL to share with mail engineers or security teams.
How It Works
Generate one unique address at 1.testonemail.com,
send emails from any provider, and watch the full diagnostic reports arrive in real time.
No account required, no paywalls, no limits.
Test One Mail is a free, lightweight email authentication diagnostic tool. We aim to remain the simplest, fastest, and most transparent option for engineers verifying their email infrastructure.