How to connect a DID number to Microsoft Teams

By DIDNumbers Team · 3 min read

Microsoft Teams can replace a traditional desk phone system, but it needs phone numbers and a connection to the phone network. Microsoft offers Calling Plans, Operator Connect and Direct Routing. With Direct Routing you bring your own numbers from any provider and connect them through a Session Border Controller (SBC). Here’s how it fits together.

What you need

  • Microsoft 365 licences that include Teams Phone for each user who will make or receive calls
  • A certified SBC, either your own or a hosted one from a partner
  • DID numbers delivered over SIP to that SBC
  • Admin access to the Teams admin centre and PowerShell

How the call flows

  1. A customer dials your number, for example a London 020 DID.
  2. The call reaches the number’s operator, which sends it over SIP to your SBC.
  3. The SBC forwards the call to Microsoft’s Teams infrastructure over TLS.
  4. Teams rings the user, auto attendant or call queue assigned to that number.

Outbound calls follow the same path in reverse.

Setup overview

  1. Point your DIDs at the SBC. In your number provider’s portal, set each number’s destination to the SBC’s SIP address.
  2. Pair the SBC with Teams. In the Teams admin centre, add the SBC by its fully qualified domain name, which must match its TLS certificate.
  3. Create voice routing. Define PSTN usages and voice routes so outbound calls leave via the SBC, and assign a voice routing policy to users.
  4. Assign numbers. Give each user, auto attendant or call queue its number in E.164 format, for example +442079460123.
  5. Test both directions, including calls from mobiles and from abroad.

Tips from real deployments

  • Use E.164 everywhere. Most “number not found” issues come from inconsistent formatting. See E.164 explained.
  • Plan for failover. Configure a second SBC or a fallback destination, such as a mobile, so calls still land if Teams or the SBC is unreachable. See smart routing.
  • Mix countries freely. A single tenant can hold numbers from many countries, so a UK sales team and a German support team can share one Teams deployment.

Frequently asked questions

Can I keep my numbers if I leave Teams later?

Yes. With Direct Routing the numbers stay on your account with the number provider. You just point them somewhere else.

Do I need an SBC for every office?

No. One SBC, or a redundant pair, can serve users in many locations and countries.

Get numbers for your Teams rollout

Browse numbers