Overview
It was confirmed on March 27, 2026, that Microsoft applied a patch to correct how Exchange Online enforces Exchange Web Services (EWS) access. Previously, some environments were able to access mailboxes via EWS even when it was not explicitly enabled (i.e., $Null status). After Microsoft corrected this behavior, EWS must now be explicitly enabled at both the organization and mailbox levels for Archive Mailbox backups to succeed.
Review this Microsoft blog post for reference: The way to control EWS usage in Exchange Online is changing.
Note: EWS is currently the only supported API that provides direct access to Archive Mailbox data. As a result, Archive Mailboxes in this state are not accessible by x360Cloud, and subsequent discovery and backup jobs will not run correctly for these mailboxes. Regular (primary) mailboxes are not impacted, as x360Cloud uses Microsoft Graph API to retrieve their data.
Solution
To address the root cause of the problem, confirm and configure EWS access to be explicitly enabled at both the organization and mailbox level.
Review the EWS enablement status at both the Organization and Mailbox level using the following PowerShell commands:
#Get the organization's EwsEnabled state.
Get-OrganizationConfig | Fl EwsEnabled
#Get all mailboxes where EwsEnabled state is not set to $true.
Get-CASMailbox -ResultSize Unlimited | Where-Object { $_.EwsEnabled -ne $true } | Select-Object Identity, PrimarySmtpAddress, EwsEnabled
If the output results for either org or mailbox are anything other than an explicit True, access via EWS must be enabled using the following commands:
#Set the organization's EwsEnabled state to $true.
Set-OrganizationConfig -EwsEnabled $true
#Bulk set EwsEnabled to $true for all mailboxes where it is not already set to $true.
Get-CASMailbox -ResultSize Unlimited | Where-Object { $_.EwsEnabled -ne $true } | Set-CASMailbox -EwsEnabled $true
If preferred, archive mailboxes may be individually modified using the following command:
#Granularly set a single mailbox's EwsEnabled state to $true
Set-CASMailbox mailbox@address.com -EwsEnabled $true
Note: New values may take up to 24 hours to replicate and take effect.
Re-check the backup status for impacted archive mailboxes; it must transition from “Unavailable” back to “Successful”. Also, you may notice that the system automatically stopped mistakenly attempting to back up archive mailboxes that are not enabled in Microsoft 365.