A Practical Microsoft 365 Security Assessment Checklist for Mid-Market Teams

Microsoft 365 sits at the center of most mid-market organizations — email, files, identity, Teams, and increasingly Copilot all run through it. That also makes it one of the highest-value targets and one of the easiest places to accumulate quiet misconfigurations. A structured Microsoft 365 security assessment turns "we think we are fine" into a prioritized, evidence-based picture of risk.

Below is a practical checklist mid-market teams can use to sanity-check their tenant. It is organized by the areas that most often surface real findings.

1. Identity and access

• Is multi-factor authentication enforced for all users, including admins and service accounts?

• Are legacy authentication protocols (which bypass MFA) blocked?

• Are Conditional Access policies in place for risky sign-ins, unmanaged devices, and location?

• How many Global Administrators exist, and is privileged access time-bound rather than standing?

2. Email and collaboration

• Are anti-phishing, safe links, and safe attachments configured in Defender for Office 365?

• Are external sharing defaults for SharePoint and OneDrive appropriate for your data sensitivity?

• Is auto-forwarding to external domains restricted?

• Are DKIM, SPF, and DMARC correctly configured for your domains?

3. Data protection

• Are sensitivity labels and DLP policies applied to regulated data (PHI, PII, financial)?

• Do you have visibility into where sensitive data actually lives across the tenant?

• Is retention configured to meet your compliance obligations?

4. Monitoring and response

• Is unified audit logging turned on and retained long enough to investigate incidents?

• Are alerts routed somewhere a human actually reviews them?

• Do you have a defined process for responding to a compromised account?

From checklist to prioritized action

A checklist tells you what to look at; it does not tell you what to fix first. The value of a formal assessment is prioritization — mapping each finding to its real-world risk and effort so leadership gets an executive-ready summary and the technical team gets a concrete remediation roadmap.

Regent Atlas is built to do exactly that: structured Microsoft 365, Azure, AWS, and identity assessments that produce prioritized findings and executive-ready reports — and Regent Forge can help implement the fixes when your team needs hands-on support.

Not sure where your tenant stands? Request a focused Microsoft 365 security assessment and start with the highest-priority risks.