Indicates that the AddressList object cannot be modified. The IsReadOnly property refers to adding and deleting the entries in the address book container represented by the AddressList object. The property is True if no entries can be added or deleted. The property is False if the container can be modified, that is, if address entries can be added to and deleted from the container.
The IsReadOnly property refers to the address book entries in the context of the address book container. It does not indicate whether the contents of the individual entries themselves can be modified.
expression Required. An expression that returns an AddressList object.