After your mailbox is moved to Microsoft Office 365 dedicated/ITAR (vNext), mail that's forwarded or redirected to other users isn't delivered. Additionally, your forwarding rule is disabled, or you receive the following error message when your change rules:
One or more rules cannot be uploaded to Microsoft Exchange and have been deactivated. This could because some of the parameters are not supported, or there is insufficient space to store all of your rules.
Use a distribution group if you have to forward or redirect messages to more than 10 users at a time. A distribution group is considered a single recipient.