Seamless Microsoft Teams Integration with Your VoIP System

320 Million Reasons This Matters

Microsoft Teams reached 320 million monthly active users in FY2024 Q1 — making it the most widely deployed enterprise collaboration platform on the planet. Approximately 80% of the Office 365 install base uses Teams, and 77% of Fortune 500 companies have standardized on it (Microsoft, 2024). If your organization uses Microsoft 365, your employees almost certainly have Teams open right now.

The natural next question is: can Teams replace your phone system entirely? For many businesses, the honest answer is: not quite. And for the ones that have tried, the experience has been instructive.

Teams as a Collaboration Tool vs. a Phone System

Teams excels at what it was designed to do: internal messaging, video meetings, file collaboration, and app integration across Microsoft's ecosystem. Where it shows its limitations is in replacing a full-featured PBX for external calling. According to Nemertes Research, 48% of Teams users require PSTN connectivity — the ability to make and receive calls to and from regular phone numbers — and that need is met in three primary ways, each with trade-offs.

Option 1: Microsoft Calling Plans

Microsoft sells PSTN connectivity as an add-on to Microsoft 365. Domestic Calling Plans cost approximately $12–$24/user/month, international plans more. For organizations needing basic outbound/inbound calling on a small scale, this works. The limitations emerge at scale: no advanced call queuing, limited IVR capabilities, no call recording without additional licensing, and no support for the kind of contact center functionality that sales or support teams depend on. Metrigy research found that companies using Microsoft Calling Plans pay 20–40% more per user than those using third-party SIP trunking or Direct Routing.

Option 2: Teams Phone with Direct Routing

Direct Routing allows businesses to connect their own SIP trunk (from a carrier like Interlink or a major telecom) to Teams via a Session Border Controller (SBC). This delivers PSTN calling through Teams at carrier-competitive rates, with number portability from existing numbers. The trade-off: SBC configuration and management requires expertise, and Teams Phone still lacks many advanced PBX features — sophisticated multi-level IVR, wallboard reporting, call monitoring, and advanced queue analytics.

Option 3: Interlink + Teams Integration (The Hybrid Approach)

The most capable configuration for organizations that need both Teams collaboration and enterprise telephony is integrating Interlink with Microsoft Teams. In this model, Interlink handles all the PBX heavy lifting — call routing, queuing, IVR, recording, analytics, CRM integration — while Teams remains the internal collaboration layer. Users make and receive external PSTN calls directly from the Teams interface, with Interlink operating invisibly in the background as the carrier and call control engine.

This architecture delivers the best of both platforms. Teams users get the calling button they're already familiar with. The business gets Interlink's enterprise-grade call center capabilities, without paying Microsoft's per-user calling plan markup. Gartner found that 91% of enterprise Teams deployments require hybrid PBX features that Teams Phone alone cannot provide — making third-party integration the norm rather than the exception at enterprise scale.

Direct Routing: How Interlink Implements It

Interlink's Teams Direct Routing integration connects your Interlink-managed VoIP infrastructure to Teams via a certified SBC. Once configured:

• External calls ring in Teams exactly as internal calls do — same interface, same notification, no separate app.
• Outbound calls made from Teams display your business number to the recipient.
• Your existing phone numbers are preserved — no number change required.
• Interlink's full routing rules, call recording, and analytics apply to all Teams calls.
• Users without Teams licenses can still use Interlink desktop or mobile softphones — the two systems coexist on the same dial plan.

The Teams Direct Routing market is growing at over 40% year-over-year as organizations that standardized on Teams for collaboration now seek a cost-effective way to add PSTN calling without paying Microsoft's per-user calling plan premium.

Compliance and E911 in a Teams Environment

One area where Teams Direct Routing has a clear operational advantage over Microsoft Calling Plans is emergency calling. KARI's Law and RAY BAUM's Act require that multi-line telephone systems (MLTS) — which includes Teams deployments — route 911 calls to a PSAP with accurate dispatchable location information, and notify an on-site party when a 911 call is placed.

These requirements are technically complex in a distributed environment where employees might be working from home, a satellite office, or a hotel. Interlink's managed SBC handles E911 compliance across all locations, updating location data as your team's footprint changes, without requiring manual maintenance of location records in the Teams admin center.

The Cost Case for Integration vs. Calling Plans

For a 50-person organization:

• Microsoft Teams Phone Essentials + Domestic Calling Plan: ~$24/user/month = $1,200/month
• Interlink managed VoIP + Teams Direct Routing: ~$22/user/month = $1,100/month

The cost difference is modest at 50 users. The capability difference is not: Interlink + Direct Routing delivers call queuing, IVR, call recording, Grafana analytics, CRM integration, and call monitoring that Microsoft's native calling plans can't match without additional third-party licensing that often costs more than the integration itself.

Sources

• Microsoft — FY2024 Q1 Earnings Report
• Microsoft — Microsoft 365 Commercial Deployment Stats, 2024
• Nemertes Research — Teams PSTN Connectivity Study
• Metrigy — Microsoft Teams Calling: Costs & Capabilities, 2024
• Gartner — Unified Communications Market Guide, 2024