unable to send email.
 

I wonder if anyone can help.

We are using outlook 2003 + Exchange Server 2003 with SP2. An number of our
users have an additional email profile which gives the user access to a
shared mailbox.

When any users attempts to send a new email, reply or forward an existing
email from the shared mailbox the following error is displayed:

"You do not have permission to send the message on behalf of the specified
user"

I have searched for this error on the KB and found KB:247909, but this seem
to relate to exchange 5.5 not 2003. Besides the solution to delete the
contents of the from field dosnt solve my problem.

Can anyone help with this?