Anon:
You don't indicate what version of Office you are running. However, since
Office 2000, there has been an option in the installation program, provided
that you select "Custom Install" to include the "Outlook Messaging
Components". In Office 2000 these were optional components; since Xp they
were included by default. You may need to simply reinstall or use the
detect and repair option to reinstall that dll from the CD if it was
originally installed, otherwise load your CD and add that optional
component.
HTH
Steve Arbaugh
MS Access MVP