Microsoft 365 security: 8 settings every company should check

Microsoft 365 is secure only when it is configured. These settings close the most common gaps in email and cloud accounts.

Many companies moved email and documents to Microsoft 365 and assume security is now Microsoft's job. Microsoft protects the platform, but how accounts, sharing and email are configured is the customer's responsibility. A few settings make a big difference.

The checklist

  1. MFA for all users — enable Security Defaults or Conditional Access policies.
  2. Block legacy authentication (old protocols such as POP, IMAP and basic SMTP authentication) that bypass MFA.
  3. Separate administrator accounts — admins use a normal account for daily work and a dedicated, protected account for administration.
  4. Block automatic forwarding of email to external addresses — a favorite trick after an account takeover.
  5. Limit external sharing in SharePoint and OneDrive, and set expiry dates for sharing links.
  6. Turn on the audit log and alerts for suspicious sign-ins and new inbox rules.
  7. Configure SPF, DKIM and DMARC for your domain.
  8. Back up Microsoft 365 data — deleted or encrypted data is not always recoverable from the recycle bin.

Check regularly

Microsoft Secure Score in the admin portal shows recommended improvements. Review it monthly, together with the list of users with administrator roles and active guest accounts.

The cloud does not remove responsibility — it changes where you need to look.

Need help with this? Contact CySec for a free consultation.

Frequently asked questions

Is Microsoft 365 secure by default?

Microsoft secures the platform, but many important settings — MFA, external sharing, forwarding rules, legacy authentication — depend on your configuration and licence.

Do we need a separate backup for Microsoft 365?

It is strongly recommended. Retention and the recycle bin help with recent deletions, but they are not a full backup against ransomware, malicious admins or long-term mistakes.

What is Secure Score?

A score in the Microsoft 365 Defender portal that lists recommended security improvements for your tenant and shows how much each one helps.

Which licence do we need for Conditional Access?

Conditional Access requires Microsoft Entra ID P1, included for example in Microsoft 365 Business Premium. Without it, use Security Defaults.


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