Post-Office 365 migration: Convert mailboxes to mail-enabled users

April 14, 2017

After moving to Office 365 you’ll want to decommission Exchange from your domain, but uninstalling Exchange removes externalemailaddress and proxyaddress properties from user accounts which are needed for Azure AD Connect to sync on-prem AD to Azure AD.

So that your Office 365 email addresses don’t become user@domain.onmicrosoft.com, here’s what I’ve been doing for our clients. I hope it helps you, too.

  1. Pause AD Connect syncing
    1. Launch powershell on AD Connect server
    2. Import-Module ADSync
    3. Set-ADSyncScheduler -SyncCycleEnabled $false
  2. Convert mailboxes to mail-enabled users
    1. In EMC, select all user mailboxes then Disable them
    2. $enableusers = Get-user -Filter { RecipientType -eq “user” }
    3. $enableusers | foreach { Enable-MailUser $_ -externalEmailAddress “$($_.samaccountname)@DOMAIN.COM” }
  3. Resume AD Connect syncing
    1. Set-ADSyncScheduler -SyncCycleEnabled $true