5 Microsoft 365 Security Settings Every Business Should Check

Microsoft 365 is central to how many businesses communicate, collaborate and store information. That makes the security of the Microsoft 365 environment an important part of the wider business security picture.

1. Multifactor authentication (MFA)

Passwords can be stolen, reused or exposed through phishing. MFA adds another verification step, making a compromised password much less useful on its own.

Start with administrator accounts and then make sure ordinary user accounts are protected appropriately for the services they use.

Practical check: Review which accounts have MFA enabled, identify exceptions and understand why any exceptions exist.

2. Administrator accounts and privileged access

Administrative accounts can make significant changes to users, services, security settings and data. They should therefore be treated differently from ordinary day-to-day accounts.

A common improvement is to reduce unnecessary privilege and make sure administrative access is controlled, reviewed and used only when needed.

Practical check: Review your administrator list and ask whether every account still needs the permissions it currently has.

3. Legacy authentication and outdated access methods

Older authentication methods can create unnecessary security exposure because they may not support modern controls in the same way as current authentication approaches.

Businesses should understand which older protocols or applications still depend on legacy authentication before making changes, because disabling them without planning can disrupt legitimate users or systems.

Practical check: Identify applications, devices or workflows that still use older sign-in methods and plan a controlled move to modern authentication where possible.

4. Email security and anti-phishing controls

Email remains one of the most common starting points for impersonation, credential theft and malicious attachments. Microsoft 365 provides security features that can help, but they still need to be configured and reviewed.

Your wider email strategy should also consider domain authentication, message protection, suspicious-link handling and user awareness.

Practical check: Review your current email security configuration and make sure staff know how to report suspicious messages.

5. Device access and endpoint security

A secure account can still be at risk if a device is unmanaged, unpatched or poorly protected. This becomes especially important when employees work remotely or use multiple devices.

Review which devices can access company resources and whether they are appropriately protected, updated and managed.

Practical check: Know which business devices are accessing Microsoft 365 and have a clear process for new, lost, replaced and retired devices.

What else should you review?

The five areas above are a useful starting point, but Microsoft 365 security is broader than any single setting. Depending on your environment, you may also need to review:

• Conditional access and sign-in controls.
• External sharing and guest access.
• Mailbox forwarding and suspicious inbox rules.
• Security and audit logging.
• Retention and data protection requirements.
• Offboarding and access removal when staff leave.

A simple Microsoft 365 security checklist

1. Protect important accounts with MFA.
2. Review administrator roles and privileged access.
3. Identify outdated authentication dependencies.
4. Review email security and phishing protections.
5. Check which devices can access business resources.
6. Review access when employees join, change roles or leave.
7. Keep your configuration aligned with how the business actually works.

Final thoughts

Microsoft 365 security is best treated as an ongoing process rather than a one-time setup. Users, devices, applications and business requirements change, so regular reviews help keep the environment aligned with the business.

You do not have to change everything at once. Start with the areas that would have the biggest impact on your organisation and work through them in a controlled way.