MX Check · DNS-over-HTTPS

Microsoft 365 domain detection

Paste one or more domains. Each is resolved live via DNS-over-HTTPS to show what mail platform they actually run — Microsoft 365, Google, or another host. When a security gateway (Mimecast, Proofpoint, Barracuda…) fronts the mailbox, it probes SPF and autodiscover to reveal whether Microsoft is hiding behind it, so a real M365 shop never gets dismissed as "not Microsoft."

Domain	Using	Details	MX records & signals
No results yet — paste domains above and run a check.

Microsoft 365 = mail lands on Exchange Online, directly or confirmed behind a gateway. Investigate = a gateway is in front and the backend couldn't be confirmed either way — these can be M365, so they're kept, not dropped. Google / Other = a confirmed non-Microsoft platform.
Backend is revealed via MX → SPF includes → autodiscover/enterpriseregistration CNAMEs. A lone MS= token never forces a Microsoft verdict on its own. Resolver: dns.google → cloudflare-dns.com fallback. Runs entirely client-side; nothing is stored or sent anywhere else.