A lot of companies have reserved more than one domain name for their organization. Multiple of those domain name are not been used for email purpose but are a target for hackers to use them for phishing attacks.
It’s highly recommended to have at least some basic DNS records to protect the domain name for phishing.
. TXT "v=spf1 -all" . MX . 0 _dmarc. TXT "v=DMARC1; p=reject;"
The above SPF record specifies that there are no mail servers been authorized as sending mail server. The DMARC rule specifies what has to be done with non legitimate mail.
