By Chris McDuffie, Structured VP of Cloud Architecture —
There’s an important Microsoft deadline approaching that many organizations don’t realize applies to them. Importantly, it has the potential to quietly break some Microsoft 365 backups and integrations overnight.
On April 2, 2026, Microsoft is shutting down Azure Access Control Services (ACS) for SharePoint Online.
Here’s why this matters: ACS is a legacy authentication method that many backup and data protection products have been using behind the scenes to connect to your Microsoft 365 tenant — specifically for SharePoint, OneDrive, and Teams data. When it stops working, any integration still relying on it stops working. No grace period. No extension.
The good news is that the major vendors, including Cohesity, Veeam, and others, saw this coming and have supported the modern replacement (Microsoft Entra ID with certificate-based authentication) for a while now.
If you deployed or reconfigured your M365 backup solution in the last year or two, you’re likely already on the new authentication method. If you set it up before 2024 and haven’t touched it since, that’s where the risk lives. The product works fine, backups are running, no one’s looking at it — and then April 2 arrives and the SharePoint and OneDrive jobs start failing. Set it and forget it is not your friend here.
This is not a product upgrade or a re-deployment. It’s a configuration change. You need to switch the app registration in your Azure tenant from the old ACS-based credential to a modern Entra ID registration with certificate authentication, then re-authorize permissions.
The vendors provide tooling and walkthroughs to make this straightforward, but it does require someone with the appropriate admin access to execute. It’s an afternoon of work, not a project — but it does need to get done before the deadline.
I also want to flag that this isn’t limited to backup products. ACS was the go-to method for granting any third-party or custom application access to SharePoint Online.
If your organization has workflow automations, reporting tools, custom PowerShell scripts, or SharePoint Add-Ins that connect programmatically to your M365 environment, those could be using ACS too. Most organizations have more of these than they realize. Microsoft offers a free M365 Assessment tool that can scan your tenant and identify every active ACS principal, so you know exactly what’s affected and where to focus.
April 2 is a hard stop. But with some attention now, it doesn’t have to be a disruption later.
If you’re not sure whether your environment is affected, we’re happy to help. We’ll run the Microsoft 365 Assessment tool against your tenant at no cost, walk you through what it finds, and help you prioritize any remediation before April 2. Reach out to your Structured account manager or contact us at info@structured.com to schedule an assessment.
About the Author
Chris McDuffie is an IT-industry veteran with more than 35 years’ experience, including 24 years managing both enterprise infrastructure and the teams supporting it. As a consultant and strategist, he aligns business needs, budget, architecture and industry best practices to maximize positive outcomes for business. With each engagement, his significant experience with Microsoft, application delivery, secure remote work, IAM, SASE and cloud security puts clients on a much stronger footing to tackle IT problems and seize growth opportunities.