Your message has been successfully relayed to the recipients
%R

on a remote system that does not support the generation of successful
delivery receipts.  This does NOT mean that your message has actually been
placed in the recipients' mailboxes; merely that it has passed through a
part of the message transport infrastructure. In the event of a nondelivery
you should expect to receive a nondelivery notification; in the event of
successful delivery, however, you are unlikely to receive a positive
confirmation of delivery.
