Teams and Copilot Are Changing Address — Check Your Firewall

Microsoft is changing the IP address ranges used by Microsoft Teams and Copilot, according to a report from csoonline.com published on 11 September 2026. Any business that locks down its network with firewall rules needs to update those rules to keep both services running properly.

This matters for more than head office. Trades and construction firms increasingly run site meetings, supplier calls and quote approvals through Teams, and use Copilot inside Outlook and Word to draft tenders, variation orders and site reports. Both sit behind the same network rules as everything else on your system.

What it means for your hours and margin

Most owners never think about IP ranges — until a service stops working mid-call. If your IT provider, or whoever manages your network, hasn't updated the firewall to allow the new addresses, Teams calls can drop and Copilot can lose access to your files at the worst possible moment.

Worked example: a 20-person contracting firm runs client calls through Teams and uses Copilot to draft quotes from job data in Word and Excel. If the firewall isn't updated before the cutover, calls drop mid-meeting and Copilot stops pulling from company files. That's an afternoon lost chasing IT support, and a client left waiting on a quote they needed the same day. On a £50,000 contract, a dropped call at the wrong moment is not a technicality — it's a lost deal or a damaged relationship.

The fix costs nothing but a phone call. The cost of ignoring it is a broken tool exactly when you need it most.

What to do this month

• Ask your IT provider, or in-house IT, whether your firewall rules have been updated for the new Teams and Copilot IP ranges.
• If you manage your own network, check Microsoft's published IP range documentation and confirm your allow-list matches it.
• Test Teams calls and Copilot access on a quiet day, not during a client meeting or site call.
• Put a reminder in the diary to recheck in a month — Microsoft has form for staggered rollouts.