1) Do you mean in a contact record or in the 'To:' field of a message? You can certainly have a record with no email address, but I don't see how that helps solve the original question.
2) IPM.note is the Outlook Message class, indicating an EMail message form, compared to IPM.contact for a contact form, IPM.appointment for a calendar form, etc. Not to be confused with the Outlook Note, which is a non-editable form.