EH-Net

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

This is an awesome site to get info and do some digging! 

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.

I've been meaning to reply to this post for months but I keep forgetting and only remember when I'm no where near a computer.

I find DNS Stuff a great tool and use it many times per day at work. Note down at the bottom of the main page are links to the Expert (http://www.dnsstuff.com/pages/expert.htm) and Testbed (http://www.dnsstuff.com/pages/testbed.htm) pages where all the good stuff is. Don't forget DNS Report (http://www.dnsreport.com/) and finally don't forget the About You (http://www.dnsstuff.com/tools/aboutyou.ch) page to check your browser/proxy settings.