David Gerard wrote:
Although I understand there are now spam
engines that retry failed messages ...
Yes, there are, but they're still rare enough to not reduce the general
effectiveness of the method (I think I received a total of one or two
German spams). This will probably change down the road, but it's a
pretty good solution until then, at no cost and almost no possibility of
failure in the absence of a badly broken MTA.
-IK