Outlook 2007 - Dist List - Cannot see Members w/o email

I have created a comprehensive Contacts database for a small business. I
then created a Distribution List of these contacts. My conundrum is that
contacts in the db without e-mail addresses do not appear in the Members list
so that I can add them to the DL. They appear in the Contracts db, just as
I've entered them, when I search it. I'm a reasonably savvy Outlook user and
this one little [non-intuitive] thing is frustrating. I feel like this is a
matter of a simple setting. Appreciate any direction as to how I can get
these contacts into the DL. Thank you.