What command will display the mail servers for lpi.org?

(Provide command with parameters)

Answer: dig lpi.org MX -or- dig lpi.org mx

Explanation:
From the man pages:
A typical invocation of dig looks like:
dig @server name type
where:
server is the name or IP address of the name server to query. This can be an IPv4 address in dotted-decimal notation or an IPv6 address in colon-delimited notation. When the supplied server argument is a hostname, dig resolves that name before querying that name server. If no server argument is provided, dig consults /etc/resolv.conf and queries the name servers listed there. The reply from the name server that responds is displayed.
name is the name of the resource record that is to be looked up.
type indicates what type of query is required ANY, A, MX, SIG, etc. type can be any valid query type. If no type argument is supplied, dig will perform a lookup for an A record.

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The same result would be achieved with nslookup -type=MX lpi.org