If you are looking for the mx record for your email server, you can use the commanline tool in Linux, nslookup with the argument mx
Command:
Code:
nslookup -type=mx DOMAIN-NAME

Here is a detailed example, here we are looking for mx records of Gmail
Code:
dev@ubuntu:~$ nslookup -type=mx gmail.com
Server:        127.0.0.53
Address:    127.0.0.53#53

Non-authoritative answer:
gmail.com    mail exchanger = 40 alt4.gmail-smtp-in.l.google.com.
gmail.com    mail exchanger = 10 alt1.gmail-smtp-in.l.google.com.
gmail.com    mail exchanger = 30 alt3.gmail-smtp-in.l.google.com.
gmail.com    mail exchanger = 20 alt2.gmail-smtp-in.l.google.com.
gmail.com    mail exchanger = 5 gmail-smtp-in.l.google.com.

Authoritative answers can be found from:

dev@ubuntu:~$

The command to remember is, -type=mx