SPF, DKIM and DMARC | Adding Credibility to Your Domain and Preventing Spam on Sent Messages
If you are using an email address that is “[email protected]”, you can edit your DNS “SPF and DKIM”. An SPF record shows where the email came from, originating domain. An example of how an SPF record would be formatted is (v=spf1 a mx include: ~all).
DKIM is a public encryption method. This works together with SPF records. SPF records are public, so a spammer could take advantage of it ( by spoofing) by finding an IP Address Authorized to send mail and then spoof messages they send to appear as if they are coming from your domain. The DKIM record prevents this and tells the the originator that it also needs a valid encryption key.
Lastly, a DMARC Record is the ultimate fail-safe for email originating from a domain. If the DMARC is different from SPF or DKIM then you can set explicitly what to do with mail messages within the DMARC.
You can ask your Domain Registrar or Web Host Provider how to enter these and if they automatically have them set.
Here is a link on how to setup DMARC on G Suite