I just found the answer to this and tested successfully:
The message recipient simply has to left-click on the attached file, then
drag & drop over to the "contacts" icon. The list is then added to that
persons 'contacts' list.
"Matt S" wrote:
I was able to email the distribution list successfully via the insert item
command, but what does the recipient need to do in order to save the list and
be able to use it?