UserProperty Object (Outlook)
Represents a custom property of an Outlook item.
Remarks
Use UserProperties(index), where index is a name or index number, to return a single UserProperty object.
Use the Add method to create a new UserProperty for an item and add it to the UserProperties object. The Add method allows you to specify a name and type for the new property.
Note
When you create a custom property, a field is added in the folder that contains the item (using the same name as the property). That field can be used as a column in folder views.
Example
The following example adds a custom text property named MyPropName.
Set myProp = myItem.UserProperties.Add("MyPropName", olText)