The setup is simple: Exchange 2010 with Outlook 2010 clients. I've setup a distribution group to include the CEO's secretaries and have used
Set-DistributionGroup -Identity firstname.lastname@example.org -GrantSendOnBehalfTo email@example.com
However the option to change the From: field does not appear in the Outlook 2010 of secretary1. Have I misunderstood something about -GrantSendOnBehalfTo ?