DNS records and how they work

Type of dns
A
    (The record to look the IP of current domain name in the dns)
     Type   Name   Value                           TTL(cache in dns)
      A          @       208.181.204.27             1/2 hours

CNAME (Alias record map other domain to the current domain (appoints to the same IP))

    Type               Name         Value                           TTL(cache in dns)
    CNAME        www           @                                    1/2 hours

   subdomian example (sub.yourdomian.com)

   Type               Name         Value                           TTL(cache in dns)
   CNAME         sub             @                                    1/2 hours



https://www.youtube.com/watch?v=iktrnk3Nd2E

(MX record is for mail server that the current domain's DNS should lookup to )

How to: Office 365 domain verification and email configuration

https://help.hover.com/hc/en-us/articles/221933708-How-to-Office-365-domain-verification-and-email-configuration