Enable EWS tenant-wide for ODM mail migration (4378864)

On Demand Migration uses Exchange Web Services (EWS) to migrate mailboxes and public folders. Starting April 1, 2025, Microsoft is changing how it checks EWS access. With this change, you must now ensure that EWS is enabled at the tenant level when using applications that access Exchange Online resources using EWS.

Previously, Microsoft allowed EWS access to individual resources even when EWS was disabled at the tenant level, as long as EWS was enabled for the individual mailboxes in scope.

With the new behavior, Microsoft requires EWS to be enabled tenant-wide to allow any EWS access.

Using Exchange Online PowerShell, check the current EWS settings for your source and target tenants.  If either one is set to False, use PowerShell to change the setting to True.

Get-OrganizationConfig | fl EwsEnabled #Check tenant setting
Set-OrganizationConfig -EwsEnabled $true #Enable EWS tenant-wide

EWS must also remain enabled for mailboxes that On Demand Migration will process. If you have mailboxes that are not in scope for migration, you can disable EWS for individual mailboxes using Exchange Online PowerShell.

Get-CASMailbox user@domain.com | fl EwsEnabled #Check mailbox setting
Set-CASMailbox user@domain.com -EwsEnabled $true #Enable EWS for a mailbox
Set-CASMailbox user@domain.com -EwsEnabled $false #Disable EWS for a mailbox