Two Microsoft Deadlines to Put on Your Calendar Now

Two Microsoft deadlines land in the first half of 2027. Neither is an emergency today. Both get expensive if you wait until the last month.

Deadline 1: Windows Server 2016

Extended support for Windows Server 2016 ends on January 12, 2027. The January Patch Tuesday update is the last free security fix it gets. After that, every new vulnerability stays open.

Plenty of small businesses still have a 2016 server running something important: a file share, a line-of-business app, a domain controller, a print server, or the accounting database nobody wants to touch.

Microsoft does offer Extended Security Updates for Server 2016 through Azure Arc for businesses that need more time. Like Windows 10 ESU, treat it as a bridge for specific servers, not a plan.

The table above is our general guidance, not Microsoft's — the right answer depends on what's running on each server.

Deadline 2: Exchange Web Services in Exchange Online

Exchange Web Services (EWS) is an older way for apps to talk to Microsoft 365 mailboxes and calendars. Microsoft began disabling it in Exchange Online in October 2026 and will shut it off completely in April 2027. The replacement is Microsoft Graph.

You probably don't use EWS directly. But some of the tools you rely on might:

• Older Outlook add-ins and CRM integrations
• Calendar sync and room-booking tools
• Backup, archiving and e-discovery products
• Mail setups on some Apple and third-party clients

What I'd Do in the Next 30 Days

1. List every server still on 2016 — including the forgotten one in the closet
2. Write down what each one does and who depends on it
3. List every app that connects to your Microsoft 365 mail or calendars, and ask each vendor whether they still use EWS
4. Decide upgrade, replace or retire for each item
5. Put the work and the budget in Q1 — before the deadlines, not after

If you're finishing your 2027 IT budget, both of these belong in it. A planned migration is a line item. A server that stops getting patches in the middle of tax season is a crisis.