As of today, Microsoft Teams Classic is no longer operational.
The legacy app has officially been decommissioned, with all backend services disabled, all servers shut down.
For IT teams globally, this isn’t just a routine product retirement, it’s a wake-up call.
The death of Classic Teams arrives just months before another major deadline: the end of Windows 10 support in October 2025.
Together, these two shifts represent a pivotal moment for IT leaders that should force a reassessment of short-term fixes and long-term resilience.
Delayed Migrations, Compressed Timelines
Despite Microsoft flagging the end of Teams Classic more than a year ago, many organisations waited until the last possible minute to make the switch.
Some leaned on Extended Security Updates (ESUs). Others fast-tracked hardware refresh cycles. But rushed rollouts come at a cost, with user disruption, increased support tickets, and teams stretched to the brink.
Even worse, a reactive approach leaves little room to test, document, or train properly – all while the clock ticks toward the Windows 10 deadline.
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Security Risks of Legacy Systems Are Escalating
The risks tied to outdated platforms have become even more evident in the last six months.
A recent study from the UK’s Royal Institution of Chartered Surveyors found that over a quarter of UK businesses fell victim to cyberattacks over the past year.
What’s more alarming is that nearly three-quarters of business leaders anticipate their organisations will face cybersecurity disruptions within the next one to two years.
This widespread apprehension reflects the very real dangers posed by running outdated software.
With Teams Classic now completely unsupported, any lingering use opens the door to serious vulnerabilities – from data leaks and infrastructure weaknesses to damaging impacts on brand reputation.
Without vendor patches or official support, any newly discovered flaws remain unaddressed, making systems an easy target for malicious actors.
Windows 10 End-of-Life: The Next Major Challenge
For many IT leaders, Teams Classic is only the first hurdle – October 14, 2025 marks the end of support for Windows 10.
While Microsoft will continue offering paid ESUs to provide additional security patches, these are expensive temporary fixes, not substitutes for a full migration.
Depending on ESUs for too long drives up costs, erodes organisational expertise as experienced staff leave or move on, and creates growing vulnerability as unpatched systems accumulate known exploits.
This is especially problematic for companies operating in regulated sectors such as healthcare, finance, or government, where compliance with security standards is non-negotiable.
Delaying migration to a supported operating system not only heightens security risks but also complicates operational continuity and regulatory adherence.
While the deadlines are clear, many organisations struggle with migrations due to budget constraints, poor visibility into legacy dependencies, undocumented systems, and loss of institutional knowledge from staff turnover.
What should be simple upgrades become drawn-out battles with costly disruptions.
What IT Teams Must Do Immediately
If organisations haven’t fully transitioned to the new Teams, the reality is they’re already behind and potentially exposed to avoidable risks.
The new Teams client must be deployed organisation-wide, including all remote and hybrid users, while ensuring every device meets OS compatibility requirements for both the new Teams client and upcoming Windows versions.
It’s also critical to disable Teams Classic entirely via the Teams Admin Center, enforcing “New Teams Only” mode to eliminate fallback usage.
Clear communication with end users is essential to manage change smoothly, and this includes providing updated documentation, training sessions, and robust support channels.
Most importantly, IT teams must document workflows, system dependencies, and rollback plans thoroughly before vital staff knowledge walks out the door.
Acting decisively now will reduce risk exposure and pave the way for smoother technology transitions ahead.
Final Word: Act Now or Pay the Price
The shutdown of Teams Classic is a wake-up call – not just for today, but for the looming Windows 10 end-of-support deadline this October.
IT leaders must act fast and lead teams through this critical upgrade by locking down migration plans, and getting ahead of Windows 10’s retirement before it becomes an operational and security nightmare.
And with Teams set to announce another raft of updates over the coming weeks and months, any delays can risk costly downtime, security breaches, and spiralling technical debt.
