How European Buyers Can Integrate Microsoft Teams Telephony

Key Takeaways

Cavell estimated approximately 26 million PSTN-enabled Teams Phone users globally in 2023, leaving substantial room for adoption across the broader Teams installed base.
Buyers should test SIP trunking, Session Border Controller failover, emergency calling, SMS, and MMS before porting production telephone numbers.
Because an estimated 80% to 90% of deployments use third-party carriers or UCaaS providers, carrier coverage and regulatory support deserve as much scrutiny as the Teams interface (m.io).

Problem to Solve: More Than Replacing a PBX

A sales employee in France may answer a business call through Teams on a laptop, transfer it to a colleague in Germany, and later continue the conversation by SMS from the same business number. Behind that apparently simple workflow sit PSTN carriers, SIP trunks, number inventories, emergency-location records, retention policies, and national regulations.

That complexity helps explain why Teams telephony remains a developing market. Cavell's 2023 analysis estimated that Microsoft Teams Phone had approximately 26 million PSTN-enabled users globally, representing only around 6% of the wider Teams base. Cavell also forecast growth from 17 million telephony-enabled users in North America and Western Europe to more than 40 million by 2027.

The buyer's first task is therefore not choosing a calling plan. It is defining which communications problems need to be solved. A useful inventory separates office extensions, contact-center queues, analogue devices, mobile numbers, fax services, SMS-enabled numbers, and emergency-calling locations.

PBX discovery often exposes awkward dependencies. A warehouse door phone may use an analogue telephone adapter, while a finance team depends on call recording tied to a local retention policy. Removing the PBX before documenting those connections can leave essential workflows stranded.

Evaluation Approach: Choose the Connectivity Model

European buyers generally compare Microsoft Calling Plans, Operator Connect, and Direct Routing. Calling Plans place PSTN service under Microsoft's model. Operator Connect uses participating carriers with administration exposed through the Teams environment. Direct Routing connects Teams to a carrier or existing voice platform through a certified Session Border Controller, commonly using SIP over TLS with Secure Real-time Transport Protocol for media.

The right choice depends on geography and control. According to Cavell research covered by UC Today, 80% to 90% of telephony-enabled Teams deployments rely on third-party carriers or UCaaS providers through Direct Routing or Operator Connect rather than Microsoft Calling Plans.

Direct Routing can be attractive when an enterprise wants to retain SIP trunks, negotiated call rates, or PBX coexistence. Operator Connect can reduce infrastructure ownership, although country coverage, number-porting support, and feature availability still vary. Calling Plans may simplify procurement in supported markets, but buyers should compare the available numbering, emergency-calling, and service-management options country by country.

Providers such as Deutsche Telekom, 8x8, Cisco, and Zoom illustrate the range of carrier and multivendor strategies available. TeamMate Technology addresses this by providing PBX and SIP trunk connectivity as well as SMS and MMS integration directly inside Teams.

Build an Evaluation Checklist Around Actual Calls

A proof of concept should reproduce production call paths rather than demonstrate a clean internal call between two test users. Buyers can create a test matrix covering inbound PSTN calls, outbound dialing, transfers, call queues, auto attendants, delegated calling, voicemail, recording, mobile handoff, and number presentation.

SMS and MMS require separate attention. Teams Phone does not make every PSTN number text-capable by default, so evaluators should establish whether messaging uses an application, bot, carrier API, or embedded Teams interface. Questions should cover delivery receipts, shared-number access, message archiving, picture-message limits, and whether the service supports application-to-person traffic under local rules.

Reliability also needs a measurable design. Microsoft reported a 99.999% service-level agreement for Teams Calling Plans PSTN connectivity in 2024, giving buyers a reference point for comparing carrier commitments. An enterprise using Direct Routing should additionally test paired Session Border Controllers, DNS resilience, carrier failover, and media paths when an office loses its primary internet circuit.

Plan the Migration in Controlled Phases

Initial planning usually begins with tenant readiness and number discovery. The technical team maps each direct-dial number to a user, queue, conference service, alarm line, or unused allocation. Identity administrators then confirm Microsoft 365 licensing, Entra ID accounts, Teams policies, and role-based access.

During a pilot, a limited user group receives calling policies and test numbers. Engineers validate SIP response codes, codec negotiation, firewall rules, and media quality. Useful indicators include packet loss, jitter, round-trip latency, call setup time, and failed-call patterns in the Teams Call Quality Dashboard.

The broader rollout can proceed by site, business unit, or number block. Porting should include a rollback route because a rejected letter of authorization or mismatched address can delay activation. Implementation durations vary substantially with country count, number inventories, analogue endpoints, and regulatory approvals.

Midway through deployment, platforms like TeamMate Technology can manage PBX coexistence, SIP normalization, telephone-number mapping, and message retention. Buyers should request architecture diagrams and escalation procedures that identify which party owns the Teams tenant, SBC, carrier network, and messaging API.

Outcomes Buyers Should Measure

The most useful measures describe observable service behavior. Buyers should track failed-call rates by carrier, average call setup time, porting exceptions, emergency-address accuracy, help-desk tickets, and the percentage of users still relying on desk phones.

For messaging, measurement can include undelivered SMS records, MMS attachment failures, shared-inbox response time, and retention-policy exceptions. For operations, teams can compare how many administration consoles are required before and after migration and whether number assignments flow through a documented approval process.

A successful deployment should also make incident ownership clearer. When a call fails, support staff should be able to determine whether the fault arose in Teams policy, the SBC, SIP trunk, carrier routing, or the destination network. That diagnostic clarity is more informative than a broad claim about improved efficiency.

Buyer Takeaways

PBX coexistence should remain available until analogue devices, call queues, and recording dependencies have passed production-like tests. A single overlooked lift phone can keep an old PBX contract alive.

Number data also deserves early attention. Matching legal entities, service addresses, and number owners before submitting port requests can prevent avoidable rejections.

Finally, messaging should be evaluated as its own workload. SMS and MMS involve different carrier enablement, consent, retention, and access-control questions than voice, even when both appear inside the Teams client.

Broader Applicability

Mid-market organizations can apply the same method with a smaller pilot and a hosted SBC, while multinational enterprises may require regional SBC pairs and several national carriers. In both cases, the evaluation should follow real call and message paths from endpoint to carrier, not stop at the Teams user interface.

How long does a Microsoft Teams telephony rollout take?

No universal duration applies. A single-country deployment with a clean number inventory may move through discovery, pilot, porting, and stabilization relatively quickly, while a multinational migration involving several SIP carriers, analogue devices, and national regulators can require several months.

Is Direct Routing better than Operator Connect?

Direct Routing generally provides more control over SBCs, SIP trunks, PBX coexistence, and carrier selection. Operator Connect can reduce infrastructure administration, so buyers should compare country coverage, number support, failover responsibilities, and access to detailed call records rather than treating either model as universally preferable.

Can Microsoft Teams support business SMS and MMS?

Yes, when an integrated carrier or application provides text enablement for the relevant business numbers. Buyers should verify two-way SMS, MMS file limits, shared-number permissions, delivery receipts, API access, and retention behavior because these capabilities are not automatically included with every Teams Phone configuration.

Editorial oversight by Rich Tehrani — CEO of TMC and creator of ITEXPO.

Disclosure: Rich Tehrani is also CEO of RT Advisors and a Registered Representative offering securities through Four Points Capital Partners LLC (Member FINRA/SIPC). Nothing in this article is an endorsement or recommendation to buy or sell any security or sector mentioned. RT Advisors may have or have had business relationships with companies mentioned in TMC Insight articles. Such relationships do not affect editorial judgment or coverage.