DMARC

TLDR

You need to have SPF and DKIM properly established first.

(assuming your domain is 'example.com') Publish a DNS TXT record with this label:
_dmarc.example.com
and this value
v=DMARC1; p=none; rua=mailto:postmaster@example.com;

try http://kitterman.com/dmarc/assistant.html

Background

https://dmarc.org/

IETF Specification

https://tools.ietf.org/html/rfc7489

Vendors

Dmarcian

https://dmarcian.com/ is a place where you can get your reports nicely aggregated and reported. See their

• video about DMARC benefits
• Their project deployment process is spot on. It's a great example of how deploying technology into an organization is more about the people, process and cross-functional training plus 'wiki' knowledge left at the end of the process than it is about the technology alone.
• deployment checklist
• Inspector: https://dmarcian.com/dmarc-inspector/equality-tech.com
• Mission Control is their account 'dashboard'

Tools

dig any _dmarc.example.com +trace

See Also

Add a DMARC record in Google support

Domain Name System. An Named Host to IP Address lookup system

Internet Engineering Task Force = organization to make the Internet work better