An IT Director at a distribution company we work with found out about this deadline the way most people do: from a support ticket, not a Microsoft email. A sales rep’s Outlook add-in stopped letting her attach a quote from Business Central mid-thread, and the contact she’d synced from BC to Outlook six months ago had quietly vanished from the folder it used to sit in. Nothing had changed on her machine. What had changed was that her company’s Business Central environment was still two release waves behind, and Microsoft had already started tightening the plumbing underneath a feature nobody in IT had flagged as fragile.
That plumbing is Exchange Web Services, the aging protocol Outlook add-ins and contact sync in Business Central have leaned on for over a decade. Microsoft is retiring it, and the resulting Outlook integration deadline that Business Central’s own product team has set is considerably firmer than the platform-wide retirement schedule most IT leaders have heard about. If your organization runs Business Central and anyone in sales, purchasing, or accounting touches customer or vendor contacts through Outlook, this is worth twenty minutes of your attention before the end of the month.
What’s Behind the Outlook Integration Deadline
Exchange Web Services, usually shortened to EWS, is the API that has quietly connected Outlook to a long list of Microsoft and third-party applications since the mid-2000s. Microsoft first announced its deprecation back in 2018, but the timeline accelerated meaningfully after the Midnight Blizzard security incident in January 2024 pushed the company toward faster retirement of legacy authentication and API surfaces across Exchange Online. The result, as published by the Exchange engineering team, is a phased shutdown: EWS begins to be disabled globally starting in October 2026, with full disablement across all tenants by April 2027.
Business Central’s product group didn’t wait for that full window to close. Because the older Exchange-based contact synchronization and Outlook add-in deployment in Business Central depend directly on EWS calls, the team attached a much nearer deadline to its own 2026 release wave 1 features: organizations need to be on Business Central version 28.0 or later, and Microsoft has stated plainly that after October 1, 2026, Outlook add-in functionality and contact sync built on the older Exchange connection may stop working in earlier versions. That is a considerably tighter window than the broader EWS retirement calendar, and it is the one that actually matters if you’re planning around this.
What Breaks in Practice, Not in Theory
For a company still running a pre-28.0 version, the practical failure points are the ones your sales and finance teams touch daily rather than anything IT usually monitors. The Outlook add-in that lets a salesperson pull up a customer’s Business Central record, attach a quote, or check open invoice balances without leaving their inbox depends on that Exchange connection to authenticate and retrieve data. The legacy Exchange Sync. Setup page, which many mid-market Business Central customers configured years ago and then never touched again, uses EWS to keep a “Business Central” folder of synced contacts current in each user’s Outlook. Automatically tracking email correspondence against a customer record, a feature accounting and account management teams tend to rely on more than they realize until it’s gone, runs through the same plumbing.
None of this fails with a dramatic outage. It fails quietly: an add-in that used to load now times out, a contact that used to sync now sits stale, an email that used to log itself against a customer record now just sends. That’s a worse failure mode for a CIO to manage than a hard outage, because it doesn’t generate an incident ticket. It generates a slow trickle of user complaints that get diagnosed as one-off glitches for weeks before anyone connects them to a platform deprecation that IT technically knew about.
What Version 28 Actually Replaces It With
Business Central 2026 release wave 1, generally available since April 1, 2026 and auto-enabled for all users on that version, rebuilds this integration on Microsoft Graph instead of EWS. The most visible change is a new “Synchronize with Outlook” action added directly to the Contacts list, which copies selected contacts from Business Central into Microsoft 365, making them usable in both Outlook and Teams. Unlike the old Exchange Sync. Setup configuration, which required a separate admin setup flow and validated an Exchange connection before anything would sync, this action sits where sales and account teams already work, and it supports syncing in either direction if an organization wants contacts created in Outlook to flow back into Business Central.
The other change worth flagging to your security and IT operations teams directly is that Outlook add-in installation now requires a one-time additional setup step to verify the account, a deliberate friction point Microsoft added for account protection reasons rather than a bug. If your organization uses centralized deployment to push the Business Central add-in to users automatically rather than relying on individual installs, that deployment process still works, but the added verification step means it is worth testing the rollout against a pilot group rather than assuming a push that worked in 2025 will behave identically in 2026.
Who Is Actually at Risk
If your Business Central environment is a standard SaaS deployment on Microsoft’s evergreen update cadence, there’s a reasonable chance you’re already on version 28.0 or close to it, since Microsoft pushes two release waves a year to every SaaS tenant on a schedule customers don’t fully control. The organizations that should be checking their version today rather than assuming they’re covered fall into a narrower but not small group: companies running Business Central on-premises, where upgrades are a deliberate IT project rather than an automatic platform event; companies that migrated from Dynamics GP, NAV, or SL in the last two years and may still be running an early post-migration version they haven’t touched since go-live; and any organization that has deliberately delayed a release wave update because of a customization or third-party integration compatibility concern, which is common enough in manufacturing and distribution environments with heavily extended BC implementations.
Checking your version takes a few minutes: in Business Central, the Help and Support page shows the current version and build number directly, and any IT Director who can’t answer “what release wave are we on” from memory should treat that itself as a minor governance gap worth closing regardless of this specific deadline.
What to Do Before October 1
The organizations that will sail through this deadline without incident are the ones treating it as a two-part check rather than a single upgrade task. The first part is confirming the Business Central version itself, since anything at 28.0 or later already has the Graph-based integration and doesn’t need to do anything further beyond being aware the old Exchange Sync. Setup pages are being phased out and shouldn’t be reconfigured going forward. The second part, and the one that gets missed, is validating that Outlook add-in deployment and any automated email-tracking workflows actually work end to end after an upgrade, not just that the version number changed. An upgrade that technically completes but leaves the add-in’s new security verification step unaddressed for most users produces the same quiet failure pattern as not upgrading at all, just with a shorter fuse. For any organization using EWS-dependent integrations beyond Business Central itself, Microsoft’s own EWS Usage Reports in the Microsoft 365 admin center are worth a look this month, since Business Central is rarely the only application in a tenant still calling that API.
None of this requires a large project. It requires someone in IT confirming a version number, someone in sales or finance confirming the add-in still authenticates cleanly, and roughly three weeks of runway that is shrinking by the day. Routeget Technologies has walked several clients through exactly this check in the past month, and in every case the fix was smaller than the anxiety the deadline initially produced, provided someone looked at it before October 1 rather than after.
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