Step 1: Have an actual email for that domain or have a forwarder setup.
Step 2: Once you have that, go to your profile name then click the company profile.
Step 3: Click on “My Domains” tab and you’ll see options to verify the domain.
Step 4: Click on “Add & Verify Domain” and enter your email address.
Step 5: Once you’re done adding it, click on “authenticate” and this is where you need to add DNS records in your GoDaddy account or whatever hosting provider you’re using.
Step 6: Go to GoDaddy, click on manage domains and view all my domains.
Step 7: From there, click “DNS” tab, then click “Manage Zones”.
Step 8: Find your domain.
Step 9: Copy the CName which is pointing to DKIM.
Note: For Godaddy, Namecheap, and Cloudflare users when adding records, don't need to add/put your Domain, because your DNS provider already includes it automatically.
For example, If the format you're using starts with "MP1._DOMAINKEY.YOURDOMAIN.CO" it should be "MP1._DOMAINKEY" only.
Step 10: Go back to GoDaddy and click “add”.
Step 11: Paste the CName record from there and set the TTL then click “save”
Step 12: Same steps with SPF.
Step 13: Once done setting it all, click on “continue” and it will propagate.
Step 14: While propagating, you can set up the tracking domain for those subdomains that you have.
Step 15: Copy the CName and add it to your record then click continue. Then wait for it to authenticate.
Step 16: Same steps with CDN Domains, add your subdomain, copy the CName and add it your record then click continue.
Step 17: Authenticate and wait for it to propagate.
Step 18: Same steps applied to your other subdomains and then wait for it to propagate and you’re done.