Some work can't live in a Microsoft tenant.

Microsoft 365 Copilot is the most widely distributed document AI in the world. It lives inside the apps people already use (Word, Excel, PowerPoint, Outlook, Teams), reaches their documents through Microsoft Graph, and ships under enterprise contracts most large IT departments understand. Microsoft has done real compliance work, including the EU Data Boundary, Customer Lockbox, the Service Trust Portal, and no training on paid-tier prompts by default.

For employees doing internal work on documents already in SharePoint or OneDrive, Copilot is often the right answer.

When you ask Copilot to summarise a document, the document travels through Microsoft’s services. The trust set for that operation includes:

• Microsoft Corporation, as the operator of the service.
• Microsoft’s declared subprocessors, which can change with notice.
• Your tenant administrator, who controls Copilot’s access to Graph.
• Anyone in your tenant with Graph permissions to the same content.
• Whatever third-party apps your tenant has connected to Graph.
• The Customer Lockbox approver chain, when it engages.

None of that is unusual for enterprise SaaS, but it is still the trust set. For some documents, the trust set you want is “the Mac it was opened on, and nothing else.”

• Internal employee work on internal documents already in your tenant.
• Outlook drafting, Teams meeting summaries, intra-team SharePoint Q&A.
• Excel modelling against existing tenant data with no external sensitivity.
• PowerPoint drafting from a corporate template that’s already in OneDrive.
• Tenant-wide rollout where everyone’s already on Microsoft 365 anyway.

• External counsel reviewing material for a client whose tenant you don’t belong to.
• Privileged drafts, opinion work, and pre-litigation materials.
• Documents under contractual confidentiality with a third party.
• Pre-publication research, peer review, IRB-restricted data.
• Government, defence, and classified work that can’t sit in a commercial tenant.
• EU practitioners with Schrems II concerns about US-cloud processing.
• Anyone working on a Mac who simply doesn’t use the Microsoft suite.

Copilot’s main advantage is that it sits inside Word and the other Office apps as a panel, while Muet sits in the menu bar and reads whichever Word document is in front of you. The output is the same: tracked changes attributed to you, accepted or rejected in Word like any reviewer’s edits.

For work already inside Microsoft 365, Copilot is already there. For a document that arrived by email, was opened in Preview or Pages, or sits on a local volume that isn’t synced anywhere, Muet is.

Microsoft 365 Copilot is priced per user per month on top of an existing M365 licence, with usage-based metering on agentic features. If you use Copilot only for document drafting, compare the total cost.