Microsoft SharePoint Changes Access to Shared Files for External Users: How Does This Affect Your Company?

Microsoft Changes How Files Are Shared with External Users

Microsoft is introducing significant changes to how external users access shared documents via SharePoint Online and OneDrive for Business, two of the most widely used tools by businesses within Microsoft 365.

Until now, when an organization shared a document with an external user, that person could access it using a verification code sent to their email, without needing to have a guest account in the company’s Microsoft 365 environment beforehand.

However, Microsoft is gradually phasing out this authentication mechanism, replacing it with an access model based on guest identities managed through Microsoft Entra ID.

The change, announced in March 2026 and scheduled for rollout between mid-October and late November, aims to unify the management of external identities and strengthen control over access to corporate information.

What will happen to files that are already shared?

One of the main consequences of this change is that certain external users may encounter an “Access Denied” message when attempting to open SharePoint links that previously worked normally.

The impact will depend on how each user’s access has been managed:

• External users who are already listed as guests: in principle, they will continue to be able to access documents without any changes.

• Users who accessed content solely through verification codes: They may lose access to previously shared links.

• Users affected by the change: You’ll need to reshare a file with them or create their guest identity in the Microsoft 365 environment.

Once the guest identity and its permissions have been correctly set up, the user will be able to regain access to previously shared documents.

This change may particularly affect companies that use SharePoint to exchange documents with clients, suppliers, consultants, or external collaborators.

What should companies review before the change?

At Isla Cloud Solutions, we recommend preparing for this transition in advance to avoid issues that could disrupt daily operations or affect collaboration with third parties.

Key preventive measures include:

1. Review external access to SharePoint

Identify which documents, folders, and sites are shared with people outside the organization.

2. Analyze sharing reports

Use Microsoft 365 administration tools to identify external users and detect any access that relies on the previous system.

3. Notify the affected departments

Notify teams that regularly share documentation with customers, vendors, and collaborators so they are aware of the change and know how to respond to potential issues.

4. Review external access policies

Review who can share files, which users are authorized, and what restrictions apply to corporate documents.

5. Establish a guest management procedure

Define how external identities are created, monitored, and deleted within the Microsoft 365 environment.

An Opportunity to Improve Microsoft 365 Security

Although this change may cause occasional issues, it also represents an opportunity to strengthen corporate information security.

With the new model, external users are now managed as guest identities within the corporate Microsoft Entra ID environment, making it easier to enforce access policies and establish controls over their activity.

This allows organizations to move toward more structured management of their external collaborators.

Security is not just about controlling who can access a document, but also about periodically reviewing whether that access is still necessary.

Therefore, it is advisable to establish policies that address:

• Who is authorized to invite external users.

• What information can be shared outside the organization.

• How often permissions should be reviewed.

• How to manage users who haven’t logged in for months.

• When access should be revoked for former employees.

Proper management of these identities helps reduce unnecessary access and improve the protection of corporate documentation.

Isla Cloud Solutions: Microsoft 365 Environment Management and Security

At Isla Cloud Solutions, we help companies manage and protect their technology infrastructures, including Microsoft 365, SharePoint, and cloud services.

Our team of specialists in advanced systems administration, IT maintenance, and cybersecurity can help organizations review their configurations, manage permissions, and anticipate changes that may affect their operations.

The transition to a more controlled model for external identities improves security management but also requires planning to avoid unexpected disruptions.

Denied access to an important document may seem like a minor incident, but when it affects a client or vendor, it can become an operational problem.

Does your company use SharePoint or Microsoft 365 to share documents?

At Isla Cloud Solutions, we can help you review your environment’s configuration, analyze external access, and prepare your organization for these changes.

Contact our team and improve the security and management of your Microsoft 365 infrastructure.