Setting up the proper DMARC records for you domain will improve the deliverability of your emails.

Official Google Documentation

https://support.google.com/a/answer/2466563

Quick Setup

Add this TXT record to your DNS using your own domain. Please replace your_domain.com with your real domain.

Type: TXT

Name: _dmarc.your_domain.com

Content: v=DMARC1; p=none;

Example

Verify Setup

Use this tool to test your domain setup: https://toolbox.googleapps.com/apps/checkmx/

You should see this DMARC setting:

If properly setup you will see it turn green: