Using NSLOOKUP, telnetting, and other command line tools can be a pain sometimes, Dnsstuff.com offers these tools one their site in on convenient place.. I’ve found the DNSreport tool to be the most useful because it can show you everything that you need in one place. The DNSreport tool shows MX, host, and DNS records and also connects to the email servers that are listed for the domain that you’re looking up. DNSstuff.com is now changing for membership so you can only look up a few domains before your asked to sign up for the $3 per month plan, there is also an option to register and get trial memberships. I’m not sure how the trial membership is limited from the paid version because I didn’t bother to sign up.
I also found some similar tools to DNSstuff.com, IPtools.com will give you most of the tools from DNSstuff minus the DNSreport.
CheckDNS.net does the command line email server and displays the output.
Also, check out IPZapper.com