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BugZero found this defect 2212 days ago.
When attempting to add an On-Prem or Hybrid organization to Veeam Backup for Office 365 the following error occurs:
The On-Premises Exchange server does not have PowerShell authentication enabled.
The On-Premises Exchange server PowerShell must have Basic Authentication enabled. Open the Exchange Admin Center Click on "servers" Select the "virtual directories" tab From the list, select "PowerShell (Default Web Site)" or "PowerShell (Exchange Web Services website)" In the pop-up window, switch to the "authentication" tab Enable “Basic authentication”