Case study · Enterprise
Enterprise Microsoft 365 Migration: Exchange, Skype for Business & Teams Voice
Cloud transformation for 20,000+ users with enterprise voice and Direct Routing.
By Spreeze team · Published
- Users migrated
- 20,000+
- Direct Routing
- Teams voice
- Reported downtime
- Zero
Overview
Spreeze delivered a large-scale Microsoft 365 transformation for an organisation with 20,000+ users, migrating from Exchange 2016 and Skype for Business to Exchange Online and Microsoft Teams with Direct Routing.
This comprehensive migration modernised the organisation’s communication platform while maintaining business continuity throughout the transition, addressing the critical Exchange 2016 end-of-support deadline.
The challenge
The organisation needed to modernise core communication platforms while ensuring zero disruption to business operations.
- Exchange 2016 nearing end of support with growing security vulnerabilities
- Large-scale mailbox estate with 20,000+ users requiring careful migration planning
- Legacy Skype for Business infrastructure with complex voice routing requirements
- Complex enterprise voice requirements including international calling and compliance
- Need for high availability and call quality during migration period
- Minimal downtime tolerance for business-critical communication systems
What we did
Spreeze implemented a phased and controlled migration strategy, ensuring seamless transition for all 20,000+ users.
- Migration of 20,000+ mailboxes to Exchange Online using hybrid coexistence
- Coexistence planning and staged cutovers by department to minimize disruption
- Migration from Skype for Business to Microsoft Teams with comprehensive user training
- Implementation of Direct Routing with certified Session Border Controllers
- Voice policy and number management for enterprise telephony
- Adoption support and post-migration optimisation to ensure user success
Outcomes
The Microsoft 365 migration delivered a modern, secure, and scalable communication platform for the entire organisation.
- Migration of 20,000+ mailboxes to Exchange Online
- Retirement of Exchange 2016 and Skype for Business infrastructure
- Enterprise-grade Teams voice platform with Direct Routing
- Reduced infrastructure footprint and operational costs
- Improved collaboration and reliability for all users
- Secure, scalable Microsoft 365 foundation for future growth
- Zero downtime achieved during migration
Technologies
Exchange Online · Microsoft Teams · Direct Routing · Session Border Controllers · Microsoft Entra ID