To set up Google Postmaster for your Sender Domain, you need to follow these steps.
Sign in to https://postmaster.google.com. Then click on Get Started.
Click Get Started
Enter your domain URL and then click Next
Copy TXT record from Google Postmaster and paste it in your DNS Management
In your DNS Management, click Add
Select Type TXT, Name – yourdomain.com and Value – TXT Record from Google Postmaster. Then click Add record
Once the domain record is added, go to Google Postmaster Tools and click Verify
You will see the status as Verified in the Postmaster Tool
Now that the Google Postmaster Tools is configured, use it to measure your spam rate and overall health of your sender domain.