“Send on Behalf” doesn’t work for newly created user

In the circumstance where you are trying to use the “send on behalf” feature of  a newly created user you may encounter the following error:

“You do not have permission to send to this recipient. For assistance, contact your system administrator.”

The reason for this is that the Offline Address Book may not have updated yet. I believe that this happens once a day by default.

To update the Offline Address Book do the following 
1. On the Tools menu, point to Send/Receive, and then click Download
Address Book.
2. In the Offline Address Book dialog box, make sure that the Download
changes since last Send/Receive check box is checked.
3. Click OK.