Observe that MX records is relevant when someone wants to send a mail to a an emailaddress associated with a domain. The sender's email-client will have to resolve the IP address of the domains mailserver, which is in the MX record of its DNS-server.
NSLOOKUP could thus be useful for troubleshooting situations where a domain has problems receiving emails, i.e to confirm that the domain actually has an MX record and that the MX record is pointed to the correct IP address.
Note that when running:
nslookup domainname
NSLOOKUP will assume domainname is on the local network and thus will try to resolve the domainname using the internal DNS-server. This will fail but nslookup will proceed to query an external
nameserver that will present the non-authoritative answer obtained.
Example:
C:\Users\jo>nslookup www.google.com
Server: Myisp.lan
Address: 192.168.2.1:53Non-authoritative answer:
Name: www.google.com
Addresses: 82.147.54.27, 82.147.54.21, 82.147.54.16, 82.147.54.28
82.147.54.15, 82.147.54.23, 82.147.54.25, 82.147.54.26, 82.147.54.24
82.147.54.19, 82.147.54.18, 82.147.54.17, 82.147.54.29, 82.147.54.22
82.147.54.22
To use nslookup interactively and set other DNS-server than your own, enter nslookup shell ,
specify the relevant DNS-server-ip(Google DNS), specify type(MX-record) and target(google.com):
nslookup
server 8.8.8.8
set type=mx
google.com
Server: google-public-dns-a.google.com
Address: 8.8.8.8
Non-authoritative answer:
google.com MX preference = 50, mail exchanger = alt4.aspmx.l.google.com
google.com MX preference = 20, mail exchanger = alt1.aspmx.l.google.com
google.com MX preference = 40, mail exchanger = alt3.aspmx.l.google.com
google.com MX preference = 10, mail exchanger = aspmx.l.google.com
google.com MX preference = 30, mail exchanger = alt2.aspmx.l.google.com
There is also the possibility to make queries directly without first entering nslookup shell::
C:\Users\jo>nslookup -query=mx google.com
Server: Myisp.lan
Address: 192.168.2.1:53
Non authoritative answer::
google.com MX preference = 30, mail exchanger = alt2.aspmx.l.google.com
google.com MX preference = 20, mail exchanger = alt1.aspmx.l.google.com
google.com MX preference = 50, mail exchanger = alt4.aspmx.l.google.com
google.com MX preference = 40, mail exchanger = alt3.aspmx.l.google.com
google.com MX preference = 10, mail exchanger = aspmx.l.google.com
google.com nameserver = ns1.google.com
google.com nameserver = ns3.google.com
google.com nameserver = ns4.google.com
google.com nameserver = ns2.google.com
aspmx.l.google.com internet address = 74.125.136.26
alt1.aspmx.l.google.com internet address = 74.125.200.26
alt2.aspmx.l.google.com internet address = 74.125.23.26
alt3.aspmx.l.google.com internet address = 173.194.72.26
alt4.aspmx.l.google.com internet address = 74.125.25.26
ns1.google.com internet address = 216.239.32.10
ns2.google.com internet address = 216.239.34.10
ns3.google.com internet address = 216.239.36.10
ns4.google.com internet address = 216.239.38.10Query for Google nameservers:
nslookup -query=ns google.com
Server: Myisp.lan
Address: 192.168.2.1:53
Non-authoritative-answer:
google.com nameserver = ns3.google.com
google.com nameserver = ns4.google.com
google.com nameserver = ns2.google.com
google.com nameserver = ns1.google.com
ns1.google.com internet address = 216.239.32.10
ns2.google.com internet address = 216.239.34.10
ns3.google.com internet address = 216.239.36.10
ns4.google.com internet address = 216.239.38.10
Same result is also obtained via
nslookup -type=ns google.com
