ContactItem.User1 Property (Outlook)
Returns or sets a String specifying the first field on the Contacts form intended for miscellaneous use for the contact. Read/write.
The properties ContactItem.User1, ContactItem.User2, ContactItem.User3, and ContactItem.User4 map to the fields User Field 1, User Field 2, User Field 3, and User Field 4 on the Contacts form respectively. These properties are explicit built-in String properties; users can use these fields for miscellaneous purposes for the contact.