In <42F9743D(_dot_)20DA(_at_)xyzzy(_dot_)claranet(_dot_)de> Frank Ellermann
<nobody(_at_)xyzzy(_dot_)claranet(_dot_)de> writes:
wayne wrote:
"ptr:foo.com ptr:bar.com ptr:baz.com" does do something
useful.
Oh, yes, I didn't get that point. They should be counted
as three mechanisms, like "mx:foo.com mx:bar.com mx:baz.com".
But each new ptr: mechanism doesn't add more DNS lookups, while each
new mx: mechanism does. This is a critical difference.
Ok, as Stuart points out, depending on how you implement the ptr:
mechanism, it is possible that each new ptr: mechanism could do part
of the work instead of doing it all on the first one, but, again, the
critical point is that the amount of work is bounded. In general,
having 100 ptr: mechanisms isn't going to be worse than one.
-wayne