I don't consider it a problem, just a "feature" of the PDML <LOL>
It's the nature of email, not confined to the PDML. If a server is busy somewhere in the pipe, then that may make email back up and go a different route, which takes longer. While that email is on its scenic route, the originally clogged server may open up again, letting subsequent email on through on the shorter path. The later ones then arrive earlier than the earlier ones. It's a case of point A to point B, though on the Net it's point A to point Q.
thus endeth the lesson
