Cool site that allows you to gather info on all kinds of internet sites, email servers, perform numerous lookups and more. Don't take my word for it. PC Mag reports that:

This is one handy page, with tons of practical tools for Web wizards (and wannabes). Look up Whois data for any domain in several ways, check a mail server to see if it's on spam blacklists, test an e-mail address for problems, and more.

http://www.dnsstuff.com/

Don

Yeah, it's my favorite site, too. They told us about it when I was doing my Network Infrastructure class for the Beast, Microsoft exam 70-216. I've known about it since then, let's see, that was in 2000-2001. Passed 70-216 "the Beast" on my 6th time.