If after selecting the Shared Exchange Mailbox [SEM] address for the From field in a new message, send on behalf appears in the from field, and the message does not send successfully, but results in the following error message:
This message could not be sent. Try sending the message again later, or contact your network administrator. You do not have the permission to send the message on behalf of the specified user. Error is [0x80070005-0x0004dc-0x000524].
The fix may be a simple as deleting the SEM address out of the from button, and adding it back in again.
Step One: Press the black triangle next to the From label in a new message window.
Step Two: Press the X next to the SEM address.
Step Three: Press the black triangle next to the From label in a new message window again.
Step Four: Select Other Email Address and type or copy the SEM address