Few Questions

[kylespringer]

What is:

Optional MPR DNS
?

 

[bones]

MPR is Mail Policy Record. The details of this implementation can be found at:
http://www.csvmail.org/draft-otis-marid-mpr-00.html

It looks like a good antispam tool if I understand correctly. You can do the same with spf (Sender Policy framework) records which would be added to your zone file. Interesting stuff
Bones