The first thing you're going to want to do is create two users in active directory. \nOWAEnabled and OWADisabled\nYou then need to mail enabled these two groups.\nenable-DistributionGroup -Identity 'domain.internal/OU/OWAEnabled' -Alias 'OWAEnabled'\nenable-DistributionGroup -Identity 'domain.internal/OU/OWADisabled' -Alias 'OWADisabled'\nI would also hide them from the address list\n Set-Distributiongroup 'OWAEnabled' -HiddenFromAddressListsEnabled $true\nSet-Distributiongroup 'OWADisabled' -HiddenFromAddressListsEnabled $true\nFrom there add the users to their respective groups based on if you want their owa enabled or not.\nFinally once you have that all setup run the following powershell commands\nGet-DistributionGroupMember "OWADisabled" | Set-CasMailbox -OWAEnabled $False\nGet-DistributionGroupMember "OWAEnabled" | Set-CasMailbox -OWAEnabled $True