I read the QMTP protocol document and there doesn't seem to be anything
that would indicate VERP is done on messages. In fact doing this could
break things if the envelope sender address couldn't handle VERP.
Maybe QMTP should be extended in a way that allows for VERP without having
to restransmit the message body more than once. Perhaps more than one
sender address could be sent. Sender and recipient addresses would be
pair up until one list or the other was exhausted and the last one from
the shorter list would be paired with items at the end of the longer list.
