一般的には「--type=MX」のようにハイフン2個ですが、nslookupの場合、それではDNSは答えてくれません。
http://www.atmarkit.co.jp/fwin2k/win2ktips/370nslookupmx/nslookupmx.html
MX(メール)レコード
[endo@colinux ~]$ nslookup -type=MX gmail.com Server: 192.168.0.1 Address: 192.168.0.1#53 Non-authoritative answer: gmail.com mail exchanger = 40 alt4.gmail-smtp-in.l.google.com. gmail.com mail exchanger = 5 gmail-smtp-in.l.google.com. gmail.com mail exchanger = 10 alt1.gmail-smtp-in.l.google.com. gmail.com mail exchanger = 20 alt2.gmail-smtp-in.l.google.com. gmail.com mail exchanger = 30 alt3.gmail-smtp-in.l.google.com. Authoritative answers can be found from: gmail.com nameserver = ns1.google.com. gmail.com nameserver = ns2.google.com. gmail.com nameserver = ns3.google.com. gmail.com nameserver = ns4.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
Aレコード
[endo@colinux ~]$ nslookup -type=A gmail.com Server: 192.168.0.1 Address: 192.168.0.1#53 Non-authoritative answer: Name: gmail.com Address: 173.194.38.86 Name: gmail.com Address: 173.194.38.85
