The ReturnReceipt property returns the address of the
person who should receive a message indicating that the current
message has been read. Setting this property updates the
Disposition-Notification-To header field with the specified
value.
Setting the ReturnReceipt property does not automatically
cause an acknowledgement to be returned to the sender. An application
is responsible for checking to make sure the header field contains a
valid address and then generating the return receipt message.