Guide For Skype For Business Phone System

Q: Can I still use Skype for Business Server on-premises?

Skype for Business Server 2019 was under extended support until October 2025 (security patches only, no new features). After that date, no updates are released and Microsoft strongly recommends migrating to Teams.

Q: Will I lose my phone numbers during migration?

No. Phone numbers are ported from your current system to Microsoft Teams through a structured process. EPC Group configures temporary call forwarding to ensure no calls are missed during the transition.

Q: Does Teams Phone have all the features Skype for Business had?

Yes, and significantly more. Teams Phone includes all Skype for Business Phone System features plus AI-powered voicemail, Copilot meeting assistance, compliance recording APIs, and Operator Connect.

Q: Can Skype for Business users call Teams users during migration?

Yes. When hybrid connectivity is established, Skype for Business users can call and message Teams users and vice versa, which is essential for phased migrations where departments move to Teams at different times.

Errin O\'Connor

December 2025

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.

Schedule a Migration Assessment Call (888) 381-9725

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.

Microsoft Strategy: 2026 Considerations for Guide For Skype For Business Phone System

Microsoft Solutions Partner status (six designations: Data and AI, Modern Work, Infrastructure, Security, Digital and App Innovation, Business Applications) replaced the legacy Microsoft Gold Partner program in 2022. EPC Group held Gold Partner status from 2003 to 2022 (the oldest continuous Gold Partner in North America) and currently holds all six Solutions Partner designations; a credentialing footprint shared by fewer than 50 firms globally and typically used by Microsoft field teams as a vetting gate for enterprise Customer 0 nominations and named-account engagements.

EPC Group 29-year Microsoft consulting heritage matters specifically because Microsoft platform decisions today are layered on top of 25 years of architectural choices: Active Directory schema decisions from 2005 affect Microsoft Entra ID Conditional Access policy design in 2026; SharePoint 2003 information architecture decisions affect Copilot grounding quality in 2026. The firms that can navigate that depth (fewer than a dozen Microsoft Solutions Partners in North America) have a structural advantage on enterprise Microsoft migrations.

Decision factors EPC Group evaluates

Cost optimization and licensing audit
Microsoft platform capability assessment
Vendor consolidation analysis
Compliance and governance posture review
Enterprise architecture roadmap

See related EPC Group services at /services or schedule a discovery call at /contact.

Guide for Skype for Business Phone System for Fortune 500 and regulated industries

EPC Group delivers Guide for Skype for Business Phone System as a core practice within the Microsoft consulting portfolio. Engagements are led by senior architects with hands-on Fortune 500 delivery experience and a bench of hundreds of Microsoft-certified consultants spanning SharePoint, Microsoft 365, Power BI, Azure, Microsoft Copilot, and Microsoft Purview.

Every Guide for Skype for Business Phone System engagement is engineered for the regulatory and operational environment it serves. Healthcare deployments carry HIPAA controls from day one; financial services deployments meet SOC 2 and FINRA retention requirements; government deployments map to FedRAMP and CMMC controls with audit-ready evidence.

Financial services

For banks, asset managers, and broker-dealers, EPC Group engineers SOC 2 audit trails, FINRA Rule 4511 and SEC 17a-4 retention, MNPI containment, and Communication Compliance for trading floors. Microsoft Purview Audit Premium with seven-year tamper-evident retention is the standard baseline; Defender for Cloud Apps detects shadow-AI exfiltration before it reaches a compliance event.

How EPC Group engages

Six-phase methodology applied to every engagement, compressed for fixed-fee accelerators and extended for full programs.

Discovery — two-week assessment of the current estate, gap analysis, risk register, target architecture, costed remediation roadmap.
Design — senior architect produces the target topology, identity framework, Conditional Access, Purview, governance model, and security posture, reviewed by client leads.
Pilot — 25 to 100 user pilot in a real business unit. Migrate, apply baselines, test integrations, capture feedback.
Wave rollout — migrate in waves of 500 to 2,500 users with communications, training, hypercare, and a per-wave retrospective.
Adoption — role-based training, Champions network, executive sponsor enablement, metrics tracked against a measured baseline.
Operate — optional managed-services retainer for license optimization, governance reviews, security monitoring, and quarterly business reviews.

Compliance-native, not bolted on

Zero governance audit failures across 11,000-plus enterprise engagements. HIPAA, SOC 2, FINRA, FedRAMP, and CMMC controls are engineered into the tenant on day one with audit-ready evidence. The regulated-industry posture is the baseline, not an upgrade tier.

Manufacturing and energy

For multi-plant manufacturers and energy operators, EPC Group integrates Microsoft 365 with operational technology, protects intellectual property through Purview labels and Endpoint DLP, and provisions frontline workers with F1 and F3 licensing patterns. Multi-region rollouts include data residency planning and offline-capable Power Platform apps for shop-floor environments.

Engagement models

Three engagement models cover most enterprise needs. Most clients start with a fixed-fee accelerator and grow into a full program or a managed-services retainer.

Fixed-fee accelerators — Copilot Readiness, Security Hardening, Tenant Health Check, SharePoint Migration, Teams Governance. Defined scope and price. Typical range $25,000 to $150,000 over four to twelve weeks.
Project engagements — full migration or governance program with milestone-based billing. Discovery through hypercare. Typical range $150,000 to $750,000-plus over three to nine months.
Managed services — tiered retainer for ongoing operations. Named senior architect on the account. From $3,500 per month with a twelve-month minimum.

Fixed-fee accelerators with real scope

Predictable scope, predictable price, predictable outcome. Copilot Readiness, Security Hardening, Tenant Health Check, SharePoint Migration, and Teams Governance ship as defined accelerators where Big 4 firms quote open-ended time-and-materials. Most projects land in the $25K-$150K range for accelerators or $150K-$750K for full programs.

Talk to a senior architect

30-minute discovery call. No pitch deck. Call (888) 381-9725 or schedule a discovery call and a senior architect responds within one business day.

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