Dynamic Distribution Groups

I was recently working with a customer who had setup the hybrid configuration and moved some pilot users mailboxes to Exchange Online. After moving the mailboxes he stop receiving emails sent to a dynamic distribution group.

I confirmed the list of recipients in the dynamic distribution group by running the following:

The list of recipients were all UserMailbox because the dynamic distribution group was created filtering on city and RecipientType UserMailbox.

After moving mailboxes to Exchange Online the on-prem mailbox is converted to a MailUser and no longer included in the dynamic distribution group. In order to fix this you need to update the recipient filter to include MailUser objects.

In this situation we were filtering based on city and I was able to fix the problem for each site with the following:

Don’t worry about adding back any of the additional filters like:

(-not(Name -like ‘SystemMailbox{*’)) -and (-not(Name -like ‘CAS_{*’))

(-not(RecipientTypeDetailsValue -eq ‘DiscoveryMailbox’))

(-not(RecipientTypeDetailsValue -eq ‘PublicFolderMailbox’))

(-not(RecipientTypeDetailsValue -eq ‘ArbitrationMailbox’))

(-not(RecipientTypeDetailsValue -eq ‘AuditLogMailbox’))

These get automatically added back into the filter for you.

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