Microsoft Entra External Identities: B2B Collaboration for Small Businesses in Berlin

Every Berlin SMB works with external parties: clients, contractors, auditors, legal counsel, technology partners, suppliers. Giving these external users access to shared resources — SharePoint sites, Teams channels, applications — without proper identity management creates an uncontrolled access risk. Microsoft Entra External Identities provides the framework for secure, managed collaboration with people outside your organization, while keeping those external accounts within the governance scope of your Conditional Access and access review policies.

What Are Microsoft Entra External Identities?

Microsoft Entra External Identities is the identity platform for external access scenarios. It encompasses two primary use cases: B2B Collaboration (partners, contractors, and suppliers accessing your Microsoft 365 resources) and B2C (customer identity for public-facing applications). For Berlin SMBs, B2B Collaboration is the relevant capability — it allows external users to authenticate using their own identity (Microsoft account, Google account, or their organization’s Entra ID) and access specific resources in your tenant without requiring you to create and manage a separate account for them.

B2B Guest Access: How It Works

When you invite an external user as a guest to your Microsoft 365 tenant, Entra External Identities creates a guest account object in your directory. The guest authenticates using their own identity provider — their home organization’s Entra ID, a personal Microsoft account, or a federated identity — and Microsoft handles the cross-tenant token validation. From the guest’s perspective, they sign in with credentials they already have. From your perspective, they are a managed directory object to which you can assign resource permissions, apply Conditional Access policies, and run access reviews.

Guest accounts consume minimal overhead: no license assignment is required for basic collaboration access, no password to manage, no MFA enrollment unless your Conditional Access policies require it (which they should). The guest account is linked to the external identity — if the guest’s account is deleted or disabled at their home organization, their access to your resources automatically breaks.

Cross-Tenant Access Settings

Entra External Identities includes Cross-Tenant Access Settings that allow fine-grained control over which external organizations you trust and to what extent. For each partner organization (identified by their tenant ID), you can configure inbound settings (whether their users can access your resources and under which MFA trust conditions) and outbound settings (whether your users can access their resources). Trust settings determine whether you trust the guest’s home organization for MFA claims — if so, a guest who has completed MFA at their home tenant is not required to register a separate MFA method in your tenant.

For Berlin SMBs with long-term strategic partners — shared ownership with external shareholders, outsourced IT support, long-term legal counsel — configuring explicit cross-tenant trust for those specific organizations reduces access friction without sacrificing security posture.

Conditional Access for External Users

Guest accounts are subject to Conditional Access policies. This is a critical security control: it prevents the common pattern of giving an external user access to SharePoint and then having that access bypass all security controls because the guest account is not explicitly included in CA policies.

For Berlin SMBs, recommended Conditional Access policies for guest accounts include requiring MFA for all guest access (if you do not trust the home tenant’s MFA claims), applying device compliance requirements for access to sensitive SharePoint sites, and blocking access from high-risk locations or anonymizing VPNs. These policies apply identically to guest accounts as they do to internal employees — the same Conditional Access engine evaluates every sign-in regardless of whether the account is a member or guest.

Entra ID Governance: Access Reviews for Guests

Entra ID Governance’s Access Reviews feature extends to guest accounts. Periodic access reviews — quarterly or annual, depending on the sensitivity of the resources — prompt designated reviewers (typically the resource owners who invited the guests) to confirm whether each guest still requires access. Guests who are not confirmed are automatically removed. This eliminates the common problem of former contractor accounts retaining access indefinitely after an engagement ends.

For Berlin SMBs subject to ISO 27001 or GDPR audits, periodic access reviews for external accounts provide documented evidence of access control governance — a concrete answer to auditor questions about how guest account proliferation is managed.

Self-Service Guest Invitation and Approval Workflows

Entra External Identities supports configurable guest invitation policies. By default, any member user can invite guests. Best practice for Berlin SMBs is to restrict guest invitations to administrators or designated users — preventing the pattern of employees freely inviting external contacts to team workspaces without IT oversight. An approval workflow in Entra ID Governance’s Entitlement Management can require that guest invitations go through an approver before the guest receives access, creating an auditable access request trail.

One-Time Passcode Authentication

For external users who do not have a Microsoft account, Google account, or Entra ID tenant — individual contractors with personal email addresses, for example — Entra External Identities supports Email One-Time Passcode (OTP) authentication. The guest enters their email address, receives a time-limited passcode, and authenticates without creating a new account. This eliminates the previous requirement for external users to create a Microsoft account solely to access your resources, which was a common friction point and adoption barrier.

Practical Configuration for Berlin SMBs

Initial configuration steps: review and restrict the guest invitation settings to prevent uncontrolled guest proliferation, configure cross-tenant access settings for known strategic partners, ensure Conditional Access policies include guest accounts rather than targeting members only, create at least one access review for existing guest accounts to establish a clean baseline, and enable Email OTP for guests without Microsoft or social accounts. These steps bring the External Identities configuration to an enterprise-grade posture within a few hours of focused configuration effort.

Conclusion

Microsoft Entra External Identities provides Berlin SMBs with a professional, policy-driven framework for external collaboration that replaces the common informal approaches — sharing passwords, creating internal accounts for contractors, or granting blanket access without governance. Guest accounts managed through External Identities are subject to the same Conditional Access policies, access reviews, and audit logging as internal accounts, which means external access is no longer an unmonitored blind spot in the organization’s security posture. For any Berlin company that regularly collaborates with external parties and has Microsoft 365 in place, configuring External Identities properly is a direct improvement to both security and compliance standing.