Microsoft Teams Direct Routing with SIP Trunking: How It Works (2026)

Quick answer: what Teams Direct Routing is

Microsoft Teams Direct Routing lets Teams users make and receive ordinary phone calls through a SIP trunk from the carrier of your choice, instead of buying Microsoft's own Calling Plans. The pieces are a Teams Phone licence for each user, a Microsoft-certified session border controller (SBC) that sits between Microsoft's Phone System and your carrier, and a SIP trunk with the phone numbers, E911 and per-minute rates you negotiated. Direct Routing is the option that gives you the most control and, for call-heavy organisations, the lowest cost per minute; Operator Connect is the middle path where an approved operator manages the connection; Calling Plans are the simplest and most expensive per user.

This article is part of the Signalmash SIP trunking resource series: what SIP trunking is, the best providers in 2026, what it costs, SIP vs VoIP and E911 and STIR/SHAKEN for SIP.

The three ways to give Teams a dial tone

• Microsoft Calling Plans. Microsoft is the carrier. You buy a plan per user with a bundle of minutes, numbers come from Microsoft, and there is nothing to install. Simple, and priced per user regardless of how much that user calls.
• Operator Connect. A Microsoft-approved operator connects its network to Teams for you; you pick the operator in the Teams admin centre and assign numbers. No SBC to run, but only operators in Microsoft's programme qualify, and pricing is the operator's per-user or per-minute deal.
• Direct Routing. You (or a partner) run a certified SBC that connects Microsoft Phone System to any SIP trunking provider. Maximum flexibility: keep existing numbers and carrier contracts, mix Teams with a legacy PBX or a contact centre, route by cost, and pay carrier per-minute rates rather than per-user bundles.

How Direct Routing works, end to end

1. A Teams user dials a number. Microsoft Phone System, in Microsoft's cloud, decides through your voice routing policies that the call should leave through Direct Routing.
2. Phone System sends the call to your SBC over SIP with TLS for signalling and SRTP for media. The SBC must be on Microsoft's certified list (AudioCodes, Ribbon, Oracle, Cisco and others) and reachable on a public name with a valid certificate.
3. The SBC forwards the call to the SIP trunk. It converts Microsoft's requirements (TLS/SRTP, specific SIP options, media bypass if configured) into whatever your carrier expects, and applies your dial-plan rules.
4. The carrier completes the call to the public network, signs it under STIR/SHAKEN, and returns audio the same way. Inbound is the mirror image: the carrier delivers a call for one of your numbers to the SBC, which hands it to Phone System, which rings the user's Teams client.

Media can flow through the SBC or, with media bypass, directly between the Teams client and the SBC to shorten the path. Either way the SIP trunk sees a normal SIP call, which is why Direct Routing works with any competent trunk provider.

What you need

• Licences. Each calling user needs Teams Phone (included in some Microsoft 365 enterprise bundles, an add-on for others). Direct Routing itself does not require a Calling Plan.
• A certified SBC. Either an appliance or virtual SBC you run in a data centre or cloud, or SBC-as-a-service from a partner. Size it to peak concurrent calls, and give it a public DNS name and a certificate from a Microsoft-trusted authority.
• A SIP trunk. From a provider that supports SIP over TLS and SRTP to the SBC, or a secure connection to the SBC with standard SIP on the carrier side. Signalmash trunks connect to the SBC by IP authentication or credentials, carry the numbers you port or buy, and include ten calls per second of capacity.
• Phone numbers. Port your existing DIDs to the trunk provider or buy new ones, then assign them to users in Teams. Local ports typically complete in one to two weeks, toll-free in two to four.
• E911. Every number that can dial out needs a dispatchable-location address on the carrier side, and Teams' emergency calling policies need configuring so that remote and mobile users' locations are handled correctly. Kari's Law and RAY BAUM's Act apply; see the E911 and STIR/SHAKEN guide.
• An administrator comfortable with PowerShell or the Teams admin centre to create the PSTN gateway, voice routes, PSTN usages and voice routing policies.

What it costs, and when it beats Calling Plans

Direct Routing has three cost lines: the Teams Phone licence per user, the SBC (a one-off appliance or a monthly service), and the carrier's usage. On Signalmash the usage is per minute with no channel fees: $0.0068 outbound to the US, $0.0053 inbound on local numbers and $0.0018 outbound toll-free on the no-minimum plan, with numbers from $0.95 a month. Microsoft's Calling Plans are priced per user per month with a bundled allowance and overage. The break-even is simple: divide the per-user Calling Plan price by the trunk's per-minute rate, and any user who calls more than that many minutes a month is cheaper on Direct Routing; at under a cent a minute the threshold is a few hundred minutes, which most sales, support and front-desk roles exceed. Organisations with hundreds of light users often keep Calling Plans for them and use Direct Routing for the heavy callers and the contact centre, which Teams routing policies allow per user.

Common mistakes

• Buying an uncertified SBC because it "speaks SIP". Microsoft only supports certified devices, and troubleshooting an unsupported one is on you.
• Forgetting that Teams expects TLS and SRTP. A trunk that only offers plain SIP/RTP still works, but the SBC must terminate the encryption; plan for that in sizing.
• Skipping E911 configuration for home workers. Dynamic emergency calling in Teams can pass a user's current location, but only if the network sites and policies are set up and the carrier can accept the location.
• Not testing failover. Point the SBC at two trunk addresses, or run two SBCs, and pull a cable during the pilot.
• Porting numbers before the routes are proven. Cut outbound over first on new numbers, then port inbound once the trunk has carried a week of production traffic.

How Signalmash handles Direct Routing

Signalmash provides the trunk side: numbers and porting, E911 provisioning with dispatchable location, STIR/SHAKEN attestation on outbound calls, branded caller ID, and direct Tier-1 routes at the rates above. Our engineers have paired the trunk with AudioCodes and Ribbon SBCs and with SBC-as-a-service partners, and sit in a shared Slack channel during the cut-over. We are not an Operator Connect operator; Direct Routing is how Teams customers use Signalmash.

Tell us your user count, minutes and SBC plans and we will quote the trunk and walk through the Teams configuration with your admin.

People also ask

What is the difference between Direct Routing and Operator Connect?

Both connect Teams to a carrier other than Microsoft. Operator Connect is managed by a Microsoft-approved operator and configured from the Teams admin centre with no SBC to run, but only approved operators qualify. Direct Routing uses a certified SBC that you or a partner operate, works with any SIP trunking provider, and gives full control over routing, numbers and cost.

Do I need an SBC for Teams Direct Routing?

Yes. Direct Routing requires a Microsoft-certified session border controller between Phone System and the SIP trunk. It can be a physical or virtual appliance you run, or SBC-as-a-service from a partner. The SBC handles TLS/SRTP toward Microsoft and standard SIP toward the carrier.

Is Direct Routing cheaper than Microsoft Calling Plans?

For users who make more than a few hundred minutes of calls a month, usually yes, because a SIP trunk bills per minute (Signalmash lists $0.0068 outbound in the US) while Calling Plans are priced per user with a bundled allowance. For light users the Calling Plan can be cheaper and simpler; many organisations mix the two by policy.

Can I keep my existing phone numbers with Direct Routing?

Yes. Port your numbers to the SIP trunking provider and assign them to Teams users; nothing about the numbers changes for callers. Local US numbers typically port in one to two weeks and toll-free numbers in two to four.

Does Direct Routing support E911?

Yes, but it has to be configured on both sides: the carrier needs a dispatchable-location address for each number, and Teams needs emergency calling policies and, for remote workers, dynamic location settings. Kari's Law and RAY BAUM's Act apply to Teams deployments in the US like any other multi-line system.