Use nslookup to check DNS propagation and verify MX record configuration

NSLookup is a tool that can be immensely helpful when troubleshooting network connectivity issues. Here are some example uses:

1.) You want to see if the DNS change you requested in live on the primary nameserver

hopper-macbook:~ andrewhopper$ nslookup
> server dns1.noris.net
Default server: dns1.noris.net
Address: 213.95.0.65#53
> set type=a
> puma.com
Server: dns1.noris.net
Address: 213.95.0.65#53


Name: puma.com
Address: 128.167.119.25

2.) You just configured Google apps for your domain and want to verify MX records have been properly configured.

hopper-macbook:~ andrewhopper$ nslookup
> set q=mx
> hopper.biz

Server: 208.59.247.45
Address: 208.59.247.45#53

Non-authoritative answer:
hopper.biz mail exchanger = 20 alt1.aspmx.l.google.com.
hopper.biz mail exchanger = 20 alt2.aspmx.l.google.com.
hopper.biz mail exchanger = 30 aspmx2.googlemail.com.
hopper.biz mail exchanger = 30 aspmx4.googlemail.com.
hopper.biz mail exchanger = 30 aspmx3.googlemail.com.
hopper.biz mail exchanger = 30 aspmx5.googlemail.com.
hopper.biz mail exchanger = 10 aspmx.l.google.com.

Authoritative answers can be found from:
hopper.biz nameserver = NS2.SLICEHOST.NET.
hopper.biz nameserver = NS3.SLICEHOST.NET.
hopper.biz nameserver = NS1.SLICEHOST.NET.
aspmx.l.google.com internet address = 209.85.221.60
alt1.aspmx.l.google.com internet address = 72.14.247.27
alt2.aspmx.l.google.com internet address = 209.85.222.78
aspmx2.googlemail.com internet address = 209.85.135.27
NS1.SLICEHOST.NET internet address = 67.23.4.57