The SMS and MMS Relay
In Windows 10, Microsoft built an underlying framework to deeply integrate your PC with your cellular device, primarily aimed at Android users via the “Phone Link” (formerly “Your Phone”) application. To facilitate this cross-device communication, Windows includes a specific privacy setting that governs whether applications from the Microsoft Store are allowed to interface with your cellular messaging stack. This is controlled by the master toggle: “Let apps read or send messages (SMS or MMS).”
When this toggle is enabled, an authorized UWP app can actively intercept incoming SMS/MMS messages routed through your connected phone, read their contents, and even send outbound text messages on your behalf (which uses your cellular carrier’s texting plan). While this is the exact functionality required for a dedicated texting app or a cross-device synchronization tool, it is an extreme privacy and security risk for almost any other type of software. A rogue app with this permission could theoretically read two-factor authentication (2FA) SMS codes or silently send premium-rate text messages without your knowledge. Unless you actively use your PC as an SMS relay, you should disable this OS-level permission immediately.
How to Revoke SMS and MMS Access
You can instantly block all Microsoft Store applications from interacting with your cellular messaging data via the Privacy settings.
- Click the Start button and select the Settings gear icon (or press
Win + I). - Click on the Privacy category.
- Look at the left-hand sidebar, scroll down to the “App permissions” section, and click on Messaging.
- In the right-hand pane, locate the master toggle switch situated immediately underneath the text Let apps read or send messages (SMS or MMS).
- Click the toggle switch to turn it Off.
Once disabled, Windows will construct a strict firewall around your messaging stack. No Store app will be able to read incoming texts or dispatch outgoing SMS/MMS messages from your PC.