See this forum post:
http://forums.contribs.org/index.php/topic,40601.0.htmlThis was never an issue in the last few months on any of my servers. However, since upgrading to 7.4 this has occurred. I don't know if the bogusmx.rfc-ignorant.org sbl was included in 7.3 and older, but it is now.
I followed the directions on the previous post (only I just removed the offending sbl by copying what was in use when I checked settings rather than blindingly copying and pasting). I am having no such issues wiht godaddy and secureserver.net.
btw, they use cnames in mx records... I noticed that and had a real hard time figuring out why their dns settings looked so goofy... now I know.