Who still has access to your Microsoft 365 files?

Sharing a Teams workspace with an agency or giving a contractor access to a SharePoint folder can save hours of emailing documents back and forth. The problem often comes later: the project ends, the people change, and nobody checks whether that access is still needed.

For a growing business, external access can build up across years of projects, tenders and supplier relationships. It is rarely the result of one dramatic mistake. Someone shares a file to get a job done, and the permission remains after the job is finished.

A regular Microsoft 365 guest access review helps you answer a simple question: which people outside your business can still reach your information, and why?

What is guest access in Microsoft 365?

Guest access lets people outside your organisation collaborate in services such as Microsoft Teams and SharePoint. It can be appropriate for clients, suppliers, consultants and project partners who need ongoing access to a shared space.

External file sharing is related, but it is worth reviewing separately. A person may have been invited to a Team, granted access to a SharePoint site, or sent a link to a particular file or folder. The access they receive depends on the settings and permissions in use.

These services are connected. Microsoft notes that a Team has an associated SharePoint site, and that sharing settings across Teams, Microsoft 365 Groups and SharePoint need to be considered together. Microsoft Learn

That is why a review limited to the Teams app can miss part of the picture.

Why does access get overlooked?

Think about a common project: your business creates a Team for a website redesign. Staff invite an external designer, an agency account manager and a freelance copywriter. Files, discussions and approvals all live in one place.

Six months later, the website is live. The designer moves company, the freelancer finishes the contract and the agency assigns a new account manager. Unless someone owns the clean-up, the original guests may remain.

The same pattern appears in finance, recruitment, legal work and customer projects. As the number of workspaces grows, it becomes harder to remember which invitations were temporary and which relationships are still active.

Microsoft provides ways to review guest identities and access to groups, including recurring access reviews in supported Microsoft Entra setups. The right process and available automation will depend on your configuration and licensing. Microsoft Learn

Five things to check in a guest access review

Who are your guest users?

Start with the external accounts recorded in your Microsoft 365 environment. Identify the person, their organisation and the reason they were invited. An unfamiliar address needs investigation, but a familiar name also needs a current business reason for access.

Ask the internal owner of each relationship to confirm whether the guest still needs it. IT can identify the account; the project owner is often better placed to judge the business need.

Which Teams and groups can they access?

Membership of a Team can expose conversations and files beyond the one document someone initially wanted to share. Review memberships against the current purpose of each workspace.

A good rule is to give access to the smallest appropriate area. If a supplier only needs a set of documents, consider whether membership of a broader Team is necessary.

What has been shared through SharePoint and OneDrive?

Look at site permissions and file or folder sharing, including links that may have been created for convenience. Pay particular attention to sensitive areas, old project sites and folders that have changed purpose.

The aim is not to stop legitimate collaboration. It is to make sure the access still matches the work being done. Microsoft’s guidance explains how SharePoint and OneDrive external sharing settings interact with guest access and site-level permissions. Microsoft Learn

Who can invite new guests?

Decide who should be allowed to grant external access and what checks they should make first. If every employee can invite outside users into any workspace, it is harder to maintain a reliable record of who has access.

The answer will vary by business. A project-led company may need frequent collaboration, while another may prefer requests through designated site owners. Set a process that people can actually follow.

When should access end?

Give guest access an owner and a review date. For a short project, the end date may be obvious. For an ongoing supplier, a periodic review can confirm whether the same people still need access.

Build removal into offboarding. When a contract ends or a project closes, review the relevant Team, SharePoint site and shared files as part of the handover.

Make the review useful without disrupting work

Deleting every guest account would be quick, but it could interrupt active customer and supplier projects. Begin by identifying the resources each person uses, then confirm the need with the relevant owner.

Prioritise access to sensitive information and accounts tied to completed projects. Remove permissions that are no longer justified, correct overly broad access and document any exceptions that must remain.

It also helps to establish a naming or ownership convention for workspaces. If nobody knows who owns a Team called “Project 2024”, deciding whether its guests still need access becomes unnecessarily difficult.

For businesses that use Microsoft 365 heavily, guest reviews work best as part of wider account and permissions management. Silver Lining’s Microsoft 365 solutions cover user management and support alongside the collaboration tools themselves. Silver Lining Convergence

How often should you review external access?

There is no universal interval for every business. A reasonable starting point is to review high-risk workspaces when a project ends and run a broader periodic review of external access. Review sooner when a supplier changes, a contract ends or a sensitive site is reorganised.

The most useful outcome is a repeatable habit: someone invites the guest for a defined reason, an owner remains responsible for that access, and someone checks when the reason may no longer apply.

Keep collaboration useful and controlled

1. Teams and SharePoint are valuable because they make it easy to work with people beyond your organisation. The same ease makes permissions worth revisiting.
2. If your business cannot readily say which external users can access its Microsoft 365 information, an access review is a sensible place to start. Contact Silver Lining to discuss your Microsoft 365 setup and the way your teams share files with customers and partners.