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In the Veeam KB4821, Veeam documents upcoming enforcement changes from Microsoft that impact how backup applications interact with Microsoft 365 services such as SharePoint Online and OneDrive. This article provides a proactive support statement for users of Veeam Backup for Microsoft 365 and Veeam Data Cloud for Microsoft 365. (https://www.veeam.com/kb4821)

What’s Changing (Effective March 1, 2026)

Microsoft is updating its application throttling enforcement in Microsoft 365. Throttling limits the number of API requests a given application registration can make before being paused or slowed (returning HTTP 429-Too Many Requests/503-Server too Busy errors). For backup tools, throttling can directly slow down large-scale data operations such as SharePoint or OneDrive backups.

Traditionally, some third-party backup vendors encouraged deploying multiple application registrations for the same tenant to spread the API load and reduce throttling. However, Microsoft’s terms of use only permit a single application registration per use-case; exceeding that usage is now strictly enforced.

It is important to note that this is not specific to Veeam’s products; it affects all third-party backup vendors that use multiple application registrations to optimize backup performance.

Why This Matters for Veeam Users

This enforced throttling behaviour means:

• If you are not using multiple application registrations, you will NOT be impacted.
• No action is required from Veeam Data Cloud customers, as any extra backup applications created for the few customers who had them will be automatically removed.
• Using multiple backup application registrations in a tenant no longer provides a performance benefit and may cause unexpected throttling behaviour.
• Even if several applications were registered previously to “work around throttling,” they now fall under Microsoft’s enforcement, and all share the same throttling limits.
• If organizations are currently configured with multiple backup applications, they could see longer completion times for backups once Microsoft’s enforcement kicks in.

Guidance from Veeam

The Veeam KB article (KB4821) outlines how to identify and manage multiple application registrations:

• Within Veeam Backup for Microsoft 365, right-click an organization and choose Manage backup applications to see if extra backup applications exist.
• Extra backup applications should be removed if they are not needed, since they do not improve performance under the new throttling rules.    
• Removing a backup application from Veeam does NOT delete it from Entra ID — any orphaned application entries must be removed manually from Entra ID if no longer required.
• Veeam recommends updating to the latest platform release to benefit from ongoing improvements, including reduced API usage that helps mitigate throttling impact.
• In the screenshot below, I have taken this from my lab environment, and it only has 1 application registered. Multiple application registrations need to be removed by selecting the Application and clicking on Remove.

Script to Identify/Resolve Orgs with Multiple Backup Applications

Alongside KB4821 article, Chris Arceneaux has published a PowerShell script under the VeeamHub/powershell project called VB365-KB4821 that directly supports the KB’s recommendations – (https://github.com/VeeamHub/powershell/tree/master/VB365-KB4821)

What the Script Does

The VB365-KB4821 script automates the manual steps described in KB4821(steps I mentioned above to remove Application Registration). In a multi-tenant environment which is common for service providers, some tenants may have multiple backup application registrations configured. This PowerShell script:

• Scanning: Identifies all Microsoft 365 organizations managed by VB365 that have more than one backup application registration.
• Reporting: Outputs a list of affected tenants with details about which application registrations are present.
• Optional Cleanup: Offers the option to remove extra backup application registrations from those tenants directly in Veeam.

Importantly, the script does NOT delete the application registrations from Entra ID; it only removes them from the Veeam backup configuration. Any cleanup at the Azure level must be done separately by an administrator.

How It Helps

This community script is valuable for:

• Service Providers — who manage large numbers of VB365 tenants and need to ensure compliance quickly across all of them.
• Operations Teams — who want to automate inspection and cleanup rather than click through each tenant’s console.
• Compliance Checks — as part of regular VB365 housekeeping or when planning upgrades or migrations.

Final Thoughts

The Veeam KB4821 support statement essentially signals that:

• Microsoft is tightening throttling rules and enforcing terms of use across all tenants.
• Running multiple backup applications per tenant for the same backup use-case provides no throttling relief under the new model.
• Veeam users should identify and consolidate to a single application per use case in their VB365 deployments to align with Microsoft’s enforcement and avoid unexpected backup delays.

This repositioning makes backups more predictable and better aligned with Microsoft’s API usage policies and helps customers avoid performance slowdowns when throttling kicks in.

Published: March 3, 2026 02:25pm