Before implementing an SPF record, my mail server IP was getting put on all sorts of blacklists. People were sending mail claiming to be from my domain and it was causing me to get on the BLs; all the major ones like CBL, Barracuda, Spamhaus, etc. Anytime anyone would try and send mail to me it would be rejected. I don't use SPF for checking incoming mail, I have the mail checked against a few RBLs and anti-spam software.

Its been confrimed..the amount of thermal grease needed to suffiently cool the macbook pro doubles the weight of the computer.