Change email adresses or reply adress office365 after removing last exchange server from on-premise

The operation on mailbox “User” failed because it’s out of the
current user’s write scope. The action ‘Set-Mailbox’, ‘EmailAddresses’, can’t
be performed on the object ‘User’ because the object is being
synchronized from your on-premises organization. This action should be
performed on the object in your on-premises organization.

To Fix this while running AD Sync, try the next thing.

There are several solutions to this, but the easiest and most ready-to-go is to modify the attribute “proxyAddresses” within Active Directory Users & Computers. Follow these simple steps:

  • Open up Active Directory Users and Computers
  • Click “View,” making sure “Advanced Features” is checked
  • Locate the user and pull up their properties
  • Go to the “Attribute Editor” tab
  • Click “Filter” and “Show only attributes that have values” (not required, but recommended)
  • Locate the attribute “proxyAddresses” and click “Edit”
  • Make adjustments to the addresses in the form of smtp: and SMTP:
    and ensure you just leave one primary email address
  • Click “OK” to save the editor changes and “OK” again to save the user. Exercise caution to only change this attribute, and that you get the syntax correct for each entry.

The changes will apply during the next scheduled sync. Alternatively, you can start it manually by running the command “Start-OnlineCoexistenceSync” from the DirSyncConfigShell.




But it might happen you dont have the tab Atibute Editor. In that case download ADExplorer.
Download Download AdExplorer (244 KB)
Run now from Sysinternals Live.

Connect after install to the local domain and navigate to the user.
Find: proxyAdresses and right click, select modify.

Add a string with capital for default/reply adress. lowercase will add a alias:

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