Microsoft 365 dependency check.
Many small businesses run email, staff sign-in, files and chat through Microsoft 365. Enter your domain to see how much of your business sits on it, and what else shares that one point of failure.
If your domain's mail records point to Microsoft and your team signs in to other apps with their Microsoft account, one Microsoft 365 outage can stop email, Teams, shared files and every app that uses Sign in with Microsoft at the same time. The free scan reads your public DNS records and shows which of your critical services depend on Microsoft.
How the scanner spots Microsoft 365
- MX record. Mail for your domain is delivered to an address ending in mail.protection.outlook.com.
- SPF record. Your SPF TXT record includes spf.protection.outlook.com, which lets Microsoft send mail for your domain.
- Verification record. A TXT record starting MS=ms proves to Microsoft that you own the domain.
- Autodiscover. A CNAME for autodiscover points to autodiscover.outlook.com so Outlook can set itself up.
- DKIM. CNAMEs named selector1._domainkey and selector2._domainkey point to your onmicrosoft.com tenant.
What stops when Microsoft 365 is down
- Sending and receiving email in Outlook. Most senders retry for a while, so mail is usually delayed rather than lost, but nothing arrives while it is down.
- Teams chat, calls and meetings.
- Files in SharePoint and OneDrive, unless they are synced and available offline.
- Signing in to any other app that uses Sign in with Microsoft (Microsoft Entra ID), and approving sign-ins with Microsoft Authenticator.
Three things to set up now
- Keep emergency admin accounts. Microsoft recommends two emergency access accounts that do not depend on your usual sign-in rules, so you can still get into the admin centre when something goes wrong.
- Host your DNS somewhere else. If your DNS is also managed in Microsoft 365, move it to a separate DNS provider, so your website and other records keep working and you can redirect mail if you need to.
- Have a second way to reach people. Keep staff and key customer phone numbers somewhere outside Microsoft 365, so you can tell people what is happening during an outage.
Frequently asked questions
How does the scanner know I use Microsoft 365?
It reads the same public DNS records any mail server reads: your MX, SPF, verification and autodiscover records. It never logs in to anything.
Is depending on Microsoft 365 bad?
No. It is a reliable service used by millions of businesses. The risk is concentration: when one company runs email, sign-in and files, one outage stops all three. Knowing that lets you plan a fallback.
Where do I see if Microsoft 365 is down right now?
Microsoft publishes service status at status.cloud.microsoft, and admins see detailed incidents under Service health in the Microsoft 365 admin centre.
Want a person to check the rest?
The Resilience Check reviews what a scan from outside cannot see: who holds each login, renewals, backups and recovery, with the risks ranked and a fixed quote for any fixes. $299 USD, usually 2 to 4 business days.