The .mdbs created by Word are a special exception. (There may be one or two
other exceptions). Generally speaking what you have to do is open your data
source in the application that created it and maintains it, and add the
field there. In the case of Outlook Contacts, you can open Outlook, open
your contact, click on the All Fields tab, and click New to add your own
field.

But I haven't personally used this approach for a long time. Outlook is
quite an unusual system when used as a "database" (for example, you can add
fields to individual contacts, and there is a mechanism to add a field to
every contact, and you may need to use one rather than the other to make
this work reliably). So I would have a good look around at this method
before using it extensively. You might want to ask around in the Outlook
groups and sites such as www.slipstick.com to see what drawbacks exist.
Personally, I would also consider the security implications of putting
sensitive data in a "database" that is probably still heavily targetted by
virus authors.

Also, to use it, you have to initiate your merge from Outlook (select the
contacts folder then go into Outlook Tools|Mail Merge...). I don't think you
will "see" these fields if you try to connect using Word's Mail Merge
Wizard.

Peter Jamieson

If you start the merge from Outlook, you can merge any field available in
Outlook - including custom fields.
See http://www.gmayor.com/mailmerge_from_outlook.htm