I had a customer recently ask me about removing forwarding. There are two steps to do this the first is to remove the UI settings and the other to change the mailbox settings. The original article written for Live@edu was a little different as the rule set has changed in Office 365. I owe my efforts to the original article here.
Please use the following instructions to disable forwarding in Office 365:
1. Create new role which parent is “MyBaseOptions”
New-ManagementRole -Parent MyBaseOptions -Name NewMyBaseOptions
2. Remove some options related “forwarding” in “Set-Mailbox”
Set-ManagementRoleEntry NewMyBaseOptions\Set-Mailbox -Parameters DeliverToMailboxAndForward,ForwardingAddress,ForwardingSmtpAddress -RemoveParameter
3.Create new role assignment policy which contains “NewMyBaseOptions”
New-RoleAssignmentPolicy -Name DenyForwardingRoleAssignmentPolicy -Roles NewMyBaseOptions,MyContactInformation, MyRetentionPolicies,MyMailSubscriptions,MyTextMessaging,MyVoiceMail,MyDistributionGroupMembership,
4. Assign the new policy to the appropriate mailbox.
Set-Mailbox –Identity XXX -RoleAssignmentPolicy DenyForwardingRoleAssignmentPolicy
Of course if you have multiple user sets then create different policies and assign. For example if you want some to forward and some not to create two policies.