Ok, than your Outlook installation is broken.
I repeat:
That was not exactly what I was suggesting.
But once again, maybe I don't understand what you guys are trying to
accomplish. The way I would do it, is enable the check-dupes-option,
create a temporary folder, import the contacts and the DL there (or
sending them there as "m stroup" wants). Then copying the more-up-to-
date contacts into the same folder and in the "duplicate contact
detected"-pop-up-window that appears, you click on "update all". Then
you open the DL and click on "update now". Afterwards I guess you can
delete the contacts in the temp folder. Now you send the updated list
back to the sender.
I guess, that comes in quite handy if the DL is based on any easy
criteria, for example the same company or the same category, because
selecting the appropriate contacts is quite easy then. Otherwise you
have to select the contacts for the DL one by one, but that is one of
the shortcomings of DLs as we all know.
I am sure I don't tell you anything new here, that's why - in the
first place - I just jumped in with side note referring to that dupe-
checking-option.