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Guide For Skype For Business Phone System
Errin O\'Connor
8 min read
Skype for Business Phone System was Microsoft's enterprise voice solution that enabled organizations to replace traditional PBX hardware with cloud-based calling through Microsoft 365. With Skype for Business Online retired in July 2021 and all enterprise voice capabilities migrated to Microsoft Teams, this guide serves organizations still running Skype for Business Server on-premises and those planning their migration to Microsoft Teams Phone. At EPC Group, we have executed over 200 Skype for Business to Teams migrations for enterprises ranging from 500 to 50,000+ users, and we continue to support organizations navigating this critical transition.
Understanding Skype for Business Phone System
The Skype for Business Phone System (also called Cloud PBX) provided enterprise-grade voice features through Microsoft's cloud infrastructure:
- Cloud PBX functionality -- Auto-attendants, call queues, voicemail with transcription, call transfer, call park, simultaneous ring, delegation (boss/admin), and music on hold -- all managed through the Microsoft 365 admin center.
- PSTN connectivity options -- Microsoft Calling Plans (Microsoft as carrier) or PSTN Conferencing with on-premises PSTN connectivity through a Mediation Server and PSTN gateway.
- Client support -- Skype for Business Desktop client (Windows and Mac), Skype for Business mobile apps (iOS and Android), and certified desk phones from Polycom, Yealink, and AudioCodes.
- Enterprise Voice (on-premises) -- For Skype for Business Server deployments, Enterprise Voice provided PBX replacement with SIP trunking, Mediation Servers, and Response Group Service for call center scenarios.
Current Status and Migration Timeline
Understanding the current lifecycle status of Skype for Business is critical for planning:
- Skype for Business Online: Retired (July 31, 2021) -- All Skype for Business Online users were migrated to Microsoft Teams. The service is no longer available. Organizations that had not completed their migration were automatically moved to Teams-only mode.
- Skype for Business Server 2019: Extended support until October 14, 2025 -- This is the final on-premises version. Microsoft will not release any new versions of Skype for Business Server. Extended support provides security updates only -- no new features or non-security bug fixes.
- Skype for Business Server 2015: Extended support ended October 2025 -- Organizations still on this version should have already migrated.
- Microsoft Teams Phone: The successor -- All Phone System capabilities are now part of Microsoft Teams. Teams Phone includes everything Skype for Business Phone System offered plus significant new features (Copilot integration, AI-powered voicemail, compliance recording, Teams Rooms, Operator Connect).
Migration Paths: Skype for Business to Teams Phone
There are several supported migration paths depending on your current Skype for Business deployment:
- Direct upgrade (Skype for Business Online users) -- Already completed. Microsoft automatically upgraded all Skype for Business Online tenants to Teams-only mode. Phone System licenses and calling plans transferred automatically.
- Hybrid migration (on-premises Server to Teams) -- For organizations running Skype for Business Server on-premises, the hybrid migration path involves: (1) establishing hybrid connectivity between your on-premises server and Microsoft 365, (2) moving users from on-premises to Teams in batches using Move-CsUser PowerShell commands, and (3) decommissioning on-premises servers after all users are migrated.
- Direct migration (fresh Teams deployment) -- Some organizations choose to deploy Microsoft Teams independently without establishing Skype for Business hybrid. This is faster but does not preserve Skype for Business contacts and conversation history.
- Coexistence modes -- Microsoft provides several coexistence modes that control how Teams and Skype for Business interact during migration: Islands (both active simultaneously), SfBOnly, SfBWithTeamsCollab, SfBWithTeamsCollabAndMeetings, and TeamsOnly (migration complete).
Key Considerations for Phone System Migration
Voice migration is the most complex part of a Skype for Business to Teams transition. These factors must be addressed:
- PSTN connectivity transition -- If you used Skype for Business with on-premises PSTN gateways, you need to choose a Teams PSTN option: Microsoft Calling Plans, Direct Routing (reusing your existing SIP trunk provider with a Teams-certified SBC), or Operator Connect.
- Response Groups to Call Queues -- Skype for Business Response Groups must be recreated as Teams Call Queues and Auto Attendants. The functionality is similar but configuration is different. No automated migration tool exists for Response Groups.
- Analog devices -- Fax machines, elevator phones, and paging systems connected to your Skype for Business Mediation Server need Analog Telephone Adapters (ATAs) or SIP gateways compatible with Teams Direct Routing.
- E911 configuration -- Emergency calling configuration must be recreated in Teams. Teams supports dynamic E911 with location-based emergency routing, which is more capable than most Skype for Business E911 implementations.
- Compliance recording -- If you used Skype for Business compliance recording (via third-party solutions), verify your recording vendor supports Teams. Most major vendors (NICE, Verint, ASC Technologies) now offer Teams-certified recording solutions.
- Desk phones -- Skype for Business certified phones (Polycom VVX series, etc.) cannot be used with Teams Phone. New Teams-certified phones are required. Some Yealink and AudioCodes models support firmware updates for Teams compatibility.
Step-by-Step Migration Approach
- Discovery and assessment (2-3 weeks) -- Inventory all Skype for Business users, phone numbers, Response Groups, dial plans, voice policies, analog devices, and third-party integrations. Document current call flows and auto-attendant configurations.
- Network readiness (1-2 weeks) -- Perform network assessments using the Microsoft Teams Network Assessment Tool and Call Quality Dashboard. Ensure bandwidth, latency, and jitter meet Teams voice quality requirements.
- Pilot deployment (2-4 weeks) -- Migrate 50-100 users (IT staff, early adopters) to Teams Phone. Test call quality, auto-attendants, call queues, voicemail, and PSTN connectivity. Validate all scenarios before broad rollout.
- Phased migration (4-12 weeks) -- Migrate departments in waves of 200-500 users. Each wave includes pre-migration communication, user training, migration execution (Move-CsUser), post-migration validation, and support desk staffing.
- Decommission (2-4 weeks) -- After all users are migrated and validated, decommission Skype for Business Server, Mediation Servers, PSTN gateways, and remove DNS records. Archive configuration for compliance records.
Why EPC Group for Skype for Business Migration
- 200+ migrations completed -- We have migrated organizations of every size from Skype for Business to Teams, including complex multi-site deployments with thousands of phone numbers and custom integrations.
- Zero-downtime voice migration -- Our parallel deployment approach ensures no disruption to phone service during the transition. Users keep their phone numbers and calling capability throughout.
- Response Group migration expertise -- We manually recreate complex Response Group and dial plan configurations in Teams, testing every call flow before cutover.
- Compliance continuity -- We ensure compliance recording, DLP, and retention policies are configured in Teams before migrating users from Skype for Business, maintaining regulatory compliance throughout the transition.
- Post-migration optimization -- After migration, we monitor Call Quality Dashboard metrics, optimize network configurations, and fine-tune auto-attendants and call queues based on real usage data.
Still Running Skype for Business? Time Is Running Out.
Extended support for Skype for Business Server 2019 ends in October 2025. EPC Group can plan and execute your migration to Microsoft Teams Phone before support ends. Contact us for a migration assessment and timeline.
Frequently Asked Questions
Can I still use Skype for Business Server on-premises?
Skype for Business Server 2019 remains under extended support until October 14, 2025, meaning Microsoft provides security patches but no new features or non-security fixes. After that date, no updates of any kind will be released. You can continue running it at your own risk, but without security patches your server becomes increasingly vulnerable. Microsoft strongly recommends migrating to Teams before support ends.
Will I lose my phone numbers during migration?
No. Phone numbers are ported from your current carrier or on-premises system to Microsoft Teams through a structured porting process. During the transition, EPC Group configures temporary call forwarding to ensure no calls are missed. The porting process typically takes 2-4 weeks for standard numbers. Throughout the migration, your users maintain their same phone numbers with no service interruption.
Does Teams Phone have all the features Skype for Business had?
Yes, and significantly more. Teams Phone includes all core Skype for Business Phone System features (auto-attendants, call queues, voicemail, call park, delegation) plus additional capabilities: AI-powered voicemail transcription, Copilot meeting assistance, compliance recording APIs, Teams Rooms integration, Operator Connect, dynamic E911, and a rich ecosystem of third-party integrations. The only scenario where Teams may require workarounds is very complex on-premises Enterprise Voice dial plans with normalization rules, which can be replicated using Teams dial plans and Direct Routing.
Can Skype for Business users call Teams users during migration?
Yes. When hybrid connectivity is established between your Skype for Business Server and Microsoft 365, interoperability is supported. Skype for Business users can call and message Teams users and vice versa, though with some feature limitations (chat formatting, file sharing between platforms). This interop capability is essential for phased migrations where some departments move to Teams before others.
How much does the migration cost?
Migration costs depend on the complexity of your Skype for Business deployment. A straightforward migration of 500 users with basic phone features typically costs $15,000-$30,000 for consulting services. Complex migrations with 5,000+ users, multi-site deployments, custom Response Groups, contact center integration, and compliance recording can range from $75,000-$200,000. This does not include new Teams-certified desk phones (if needed) or Microsoft licensing changes. EPC Group provides detailed cost estimates after the discovery phase assessment.