How to find out the MX record for a domain on Linux?

How to find out a domain’s MX record for Email on Linux? For example, to find which domain/IP the email to gmail.com is delivered to.

You may make use of the host command.

The -t option is used to select the query type. type can be any
recognized query type: CNAME, NS, SOA, SIG, KEY, AXFR, etc.

Find out the MX record for a domain such as gmail.com:

$ host -t MX gmail.com
gmail.com mail is handled by 20 alt2.gmail-smtp-in.l.google.com.
gmail.com mail is handled by 30 alt3.gmail-smtp-in.l.google.com.
gmail.com mail is handled by 10 alt1.gmail-smtp-in.l.google.com.
gmail.com mail is handled by 5 gmail-smtp-in.l.google.com.
gmail.com mail is handled by 40 alt4.gmail-smtp-in.l.google.com.

Find out the MX record from a specific DNS server such as 8.8.8.8:

$ host -t MX gmail.com 8.8.8.8
Using domain server:
Name: 8.8.8.8
Address: 8.8.8.8#53
Aliases: 

gmail.com mail is handled by 5 gmail-smtp-in.l.google.com.
gmail.com mail is handled by 40 alt4.gmail-smtp-in.l.google.com.
gmail.com mail is handled by 20 alt2.gmail-smtp-in.l.google.com.
gmail.com mail is handled by 10 alt1.gmail-smtp-in.l.google.com.
gmail.com mail is handled by 30 alt3.gmail-smtp-in.l.google.com.