What Is an Office 365 Checker?
An Office 365 checker validates whether email and password combinations work with Microsoft's identity platform. If you manage Microsoft 365 accounts, need to verify credentials before deployment, or want to confirm account access-this tool gives you a straightforward way to test authentication.
The checker connects to Microsoft's authentication endpoints and reports whether credentials are valid, invalid, or blocked by security policies. No guesswork-you get definitive results.
How to Check Office 365 Credentials
Verification is simple:
- Enter email and password in the required format (email:password)
- For multiple accounts, add one credential pair per line
- Click Check to start the validation process
- Review results showing valid, invalid, or blocked status
- Export results if needed for documentation
Understanding Check Results
Valid (Success)
Credentials authenticated successfully. The email and password combination works with Microsoft 365. The account is active and can sign in-assuming no additional security measures like MFA are required for actual access.
Invalid (Authentication Failed)
Authentication failed. Common reasons include:
- Incorrect password
- Account doesn't exist
- Account deleted or disabled
- Typo in email address
- Password expired and requires reset
Blocked or Restricted
Some accounts may show blocked status even with correct credentials:
- MFA required: Account requires Multi-Factor Authentication, blocking basic auth
- Conditional access: Policies restrict authentication from unknown devices/locations
- Legacy auth disabled: Organization disabled basic authentication
- Account locked: Too many failed attempts triggered a security lockout
- Geographic restrictions: Sign-in blocked from your region
Common Use Cases
IT Administration
Managing a Microsoft 365 tenant means managing credentials. Use the checker to:
- Verify newly created accounts work before handing off to users
- Test password resets completed successfully
- Confirm service accounts have valid credentials
- Audit credential lists for migration projects
Migration and Onboarding
When moving users to Microsoft 365 or setting up new tenants, credential verification ensures smooth transitions. Check credentials before going live to avoid day-one access issues.
Security Auditing
Security teams can verify that compromised or shared credentials no longer work after password rotations. Confirm that disabled accounts truly can't authenticate.
Microsoft 365 Authentication Methods
Microsoft 365 supports multiple authentication approaches:
- Basic authentication: Simple username/password. Being phased out by Microsoft.
- Modern authentication: OAuth-based with support for MFA and conditional access.
- Federated authentication: Uses on-premises identity providers like ADFS.
- Passwordless: Microsoft Authenticator, FIDO2 keys, Windows Hello.
Our checker tests basic authentication. Accounts configured for modern auth only may show as blocked even with valid credentials.
Security Best Practices
When working with credentials:
- Only check accounts you own or have explicit authorization to test
- Don't store credential results-verify and discard
- Use this tool on secure networks, not public WiFi
- Be aware that multiple failed attempts may trigger account lockouts
- Treat all credential data as highly sensitive
Troubleshooting Failed Checks
All Accounts Showing Blocked
If every account shows blocked, the organization likely disabled basic authentication entirely. This is Microsoft's recommended configuration. Check your tenant settings in the Microsoft 365 admin center.
Intermittent Failures
Sometimes valid accounts fail due to temporary issues:
- Microsoft service outages (check status.office.com)
- Network connectivity problems
- Rate limiting from too many requests
- Temporary security holds on suspicious activity
Retry failed accounts after a few minutes. If issues persist, verify credentials manually through the Microsoft 365 portal.
Privacy and Data Handling
Your credential data security matters:
- Credentials are sent directly to Microsoft for authentication
- We don't store, log, or retain any credentials you check
- Results stay in your browser session only
- No credential data is transmitted to our servers
- Clear your browser after checking sensitive accounts
Frequently Asked Questions
What is Office 365 credential checking?
Office 365 credential checking verifies whether an email and password combination is valid for Microsoft 365 services. It tests authentication against Microsoft's identity platform to confirm the account exists and credentials are correct.
What Microsoft domains does this checker support?
The checker works with all Microsoft 365 domains including outlook.com, hotmail.com, live.com, msn.com, and custom domains using Microsoft 365 (formerly Office 365) for email. Any account authenticating through Microsoft's identity system is supported.
Why might valid credentials show as failed?
Several factors can cause valid credentials to fail: Multi-Factor Authentication (MFA) blocking basic auth, conditional access policies, account lockouts, regional restrictions, or Microsoft's security systems detecting unusual activity. Legacy authentication must be enabled for basic credential checks.
Is this tool safe to use?
Yes, for checking accounts you own or have authorization to verify. The tool only performs authentication tests-it doesn't access mailbox content, change passwords, or modify account settings. Use responsibly and only with proper authorization.
Can I check multiple accounts at once?
Yes. Enter credentials in email:password format, one per line. The tool processes them sequentially and reports results for each account. Batch checking is useful for IT administrators managing multiple accounts.