Microsoft 365 Security Best Practices
By the CTEKS team · October 15, 2026 · 2 min read
- Enforce MFA and block legacy sign-in.
- Filter email and authenticate your domain.
- Back up and monitor your tenant.
Microsoft 365 holds your email, files and chats, so it is a top target. The default settings are not always the safest. These steps close the most common gaps.
Protect sign-ins
- Require multi-factor authentication for every user, starting with administrators.
- Block legacy sign-in methods that cannot use MFA.
- Use conditional access to challenge sign-ins from unusual places or unmanaged devices.
- Keep the number of global administrators small, and give them separate admin accounts.
Defend against phishing
- Turn on advanced email filtering and safe links and attachments.
- Set up SPF, DKIM and DMARC for your domain so others cannot easily impersonate you.
- Train staff with short, regular phishing lessons and simulated emails.
Control data
Review who can share files outside the company. Use sensitivity labels and data loss prevention for confidential information, and set retention policies so important data is not lost.
Manage devices
Use Intune or similar tools to require encryption, screen locks and updates on devices that access company data, and to wipe a lost phone.
Back it up and watch it
Use an independent backup for mail, OneDrive, SharePoint and Teams. Turn on audit logging and review alerts so unusual activity is noticed quickly.
How CTEKS helps
We configure and manage Microsoft 365 security, from conditional access and email protection to device management and backup.
Frequently asked questions
Is Microsoft 365 secure out of the box?
It is a strong platform, but some protective settings must be turned on and tuned for your business.
Which license do we need?
It depends on the features you want. We review your licensing and recommend what fits.
What is DMARC?
It is an email setting that tells receivers how to handle messages that fail checks, helping stop others from impersonating your domain.
Our Microsoft 365 support and consulting team can review your tenant. Want a second opinion on your own setup? Request a free assessment and we will walk you through it in plain English.
Keep reading
- Migrating to the Cloud: What to Plan First
- Network Performance Problems and Security Risks
- Ransomware Protection: A Business Guide
More guides are in our knowledge base. Prefer to talk it through? See our support plans or call (847) 200-3666.
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