You need to be assigned permissions before you can perform this procedure. To see what permissions you need, see the "Mail user" entry in Mailbox Permissions.

In the Exchange Management Shell on the coexistence server, do the following to set the immutable ID of a mail user to the UPN of that mail user.

1. Retrieve the UPN of the mail user you want to configure.
   
   

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   Get-MailUser david | Format-Table Name, Alias, UserPrincipalName

2. Set an unused property on the mail user to upgrade it to a version that can be managed by the coexistence server. In this example, the ModeratedBy property is used. Respond "Yes" to the prompt asking if you want to upgrade the object.
   
   

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   Set-MailUser david -ModeratedBy administrator

3. Set the immutable ID of the mail user to the mail user's UPN.
   
   

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   Set-MailUser david -ImmutableID david@contoso.com

4. Clear the property that was set to upgrade the object. Respond "Yes" to the prompt asking if you want to upgrade the object.
   
   

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   Set-MailUser david -ModeratedBy $Null

If you don't want to set this property individually for each mailbox that's moved to the cloud, you can use the following commands to configure the mailboxes in bulk. Run these commands each time you move one or more mailboxes to the cloud.

1. Retrieve a list of all mail users that don't have a value set for the immutable ID and that also have an external e-mail address that points to the cloud-based SMTP namespace. Replace "service.contoso.com" with your cloud-based SMTP namespace, but be sure to keep the wildcard character ( * ).
   
   

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   $MailUsers = Get-MailUser -Filter {(ImmutableID -Eq $Null) -And (ExternalEmailAddress -Like "*service.contoso.com") }

2. Set the UPN on the immutable ID for each mail user that's returned. The UPN is taken from the UserPrincipalName property on the mail user and set on the ImmutableID property. This example uses the ModeratedBy property to upgrade the mail user to a version the coexistence server can manage. Choose another property if your organization already uses the ModeratedBy property.
   
   

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   $MailUsers | ForEach {Set-MailUser $_.Alias -ModeratedBy Administrator -ForceUpgrade; Set-MailUser $_.Alias -ImmutableId $_.UserPrincipalName; Set-MailUser $_.Alias -ModeratedBy $Null -ForceUpgrade}

You need to be assigned permissions before you can perform this procedure. To see what permissions you need, see the "Remote mailboxes" entry in Mailbox Permissions.

In the Shell on the coexistence server, do the following to set the immutable ID of a remote mailbox to the UPN of that mail user.

1. Retrieve the UPN of the remote mailbox you want to configure.
   
   

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   Get-RemoteMailbox david | Format-Table Name, Alias, UserPrincipalName

2. Set the immutable ID of the remote mailbox to the remote mailbox's UPN.
   
   

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   Set-RemoteMailbox david -ImmutableID david@contoso.com

If you don't want to set this property individually for each mailbox that's moved to the cloud, you can use the following commands to configure the mailboxes in bulk. Run these commands each time you move one or more mailboxes to the cloud.

1. Retrieve a list of all remote mailboxes that don't have a value set for the immutable ID.
   
   

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   $RemoteMailboxes = Get-RemoteMailbox -Filter {ImmutableID -Eq $Null}

2. Set the UPN on the immutable ID for each remote mailbox that's returned. The UPN is taken from the UserPrincipalName property on the mail user and set on the ImmutableID property.
   
   

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   $RemoteMailboxes | ForEach {Set-RemoteMailbox $_.Alias -ImmutableId $_.UserPrincipalName}

To verify that you've set the immutable ID of a mail user or remote mailbox object to the UPN of that object, use the following commands in the Shell on the coexistence server. The ImmutableID and UserPrincipalName properties should match each other.

• To view the ImmutableID and UserPrincipalName properties for a mail user, do the following.
  
  

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  Get-MailUser david | Format-Table Name, Alias, ImmutableID, UserPrincipalName

• To view the ImmutableID and UserPrincipalName properties for a remote mailbox, do the following.
  
  

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  Get-RemoteMailbox david | Format-Table Name, Alias, ImmutableID, UserPrincipalName

Having problems? Ask for help in the Coexistence and Migration forum. To access the forum, you'll need to sign in using an account that's granted administrator access to your cloud-based service. Visit the forum at: Coexistence and Migration