Granting support staff access to modify send as in Exchange 2010
The Role Recipient Management is often given to Helpdesk and Support staff who need to be able to create, modify and disable recipients in Exchange 2010. One permission which this role does not grant and may be needed is the ability to modify the “Send as” attribute on recipients.
The Active Directory Permission Role allows this access and by default is part of the Role Group Organisation Management. This Role Group grants the member complete access to Exchange and it’s likely you don’t want to grant complete access to allow them to modify the “Send as” attribute.
Instead you can create a custom Role Group that includes the Roles from Recipient Management and the Active Directory Permission group (you can also define the OU to restrict the access to only recipients within that OU).