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"Warning: Exchange account was not found"

KB ID: 4877
Product: Veeam Backup for Microsoft 365 | 8.5
Published: 2026-07-08
Last Modified: 2026-07-08
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Challenge

When backing up Exchange Online mailboxes, Veeam Backup for Microsoft 365 intermittently fails to discover and process some mailboxes, reporting the following warning:

Warning: Exchange account was not found

The affected mailboxes vary between job runs, and in some cases, only a small subset of mailboxes back up successfully. The impacted mailboxes exist, are licensed, and function normally in Microsoft 365. This behavior is typically observed in hybrid organizations after mailboxes have been migrated from on-premises Exchange to Exchange Online.

Cause

This issue occurs because the Microsoft Autodiscover response for mailboxes located in a separate forest of a multi-forest hybrid organization does not consistently return all of the attributes that Veeam Backup for Microsoft 365 requires to identify each mailbox. Because the returned attributes vary between requests, the specific mailboxes that fail to be discovered differ from one job run to the next.

Solution

A patch is available for Veeam Backup for Microsoft 365 8.5.0.1014 that resolves this issue.

Before applying the patch, ensure that Veeam Backup for Microsoft 365 has been upgraded to build 8.5.0.1014.

Download Patch

After downloading the patch, complete the following steps:

  1. Install the following .msp files in the order listed:
    1. VeeamBackupMicrosoft365_8.5.0.1503_20260702.msp
    2. VeeamExplorerForExchange_8.5.0.1503_20260702.msp
    3. VeeamExplorerForSharePoint_8.5.0.1503_20260702.msp
    4. VeeamExplorerForTeams_8.5.0.1503_20260702.msp
  2. Upgrade any remote backup proxies and proxy pools, if applicable. For instructions, see Upgrading Backup Infrastructure Components.
  3. Re-run the affected backup jobs and verify that the issue is resolved.

If this KB article did not resolve your issue or you need further assistance with Veeam software, please create a Veeam Support Case.

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