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:

