First and foremost (and to reiterate), this is an Outlook question. Please
post future questions in the Outlook discussion group. Although you may be
using Access to manipulate Outlook, you are still working with Outlook - just
not directly.
Without seeing the code, I can't answer the question. When I checked the
list of properties for an Outlook MailItem, there is no .FROM property. It
can be assumed then that Outlook was designed so that you cannot
programically create a message and make it look like it was sent from
somebody else. Likewise the .SenderEmailAddress is read-only. I do know that
the Sent on Behalf property exists for accountability purposes as in "From
David Holley Sent on Behalf of Rachel Ray".
What you'll need to do is ask the Outlook newsgroup how you can programicaly
send a message from a different Mailbox to whom you have the appropriate
rights.