// FREE TOOL
MX Record Lookup
No signup. No limits. Same continuous check we run on every managed mailbox.
What MX records route
MX records tell the internet which server receives mail for your domain. Nothing to do with sending — that's governed by SPF/DKIM and your SMTP servers.
Correct patterns
Google Workspace: smtp.google.com priority 1. Microsoft 365: your-tenant.mail.protection.outlook.com priority 0.
The invisible cold email killer
Wrong MX means campaigns send fine but replies bounce silently. You see opens and clicks but no replies — the most expensive invisible error in cold email.
Common questions
Lower is preferred. Receivers try the lowest-priority server first; higher numbers are fallbacks.
CLAYINBOX runs this check continuously on every domain it manages — automatically.