Postmaster Tools is a free online tool provided by Google that provides marketers direct access to reputation, deliverability, security and performance diagnostics straight from Gmail about your email domains and IPs.
1. Sign in to Postmaster Tools - Google Gmail
2. In the bottom right, click Add (plus sign)
3. Enter your authentication domain.
Noted: You can add either the DKIM (DomainKeys Identified Mail) domain or the SPF (Sender Policy Framework) domain.
4. Click Next.
5. May add the TXT record to the DNS zone management.
6. To prove that you own this domain, click Verify.
Noted: After verification, it may take some time before your domain’s verification status updates to “Verified.”
7. Now it show complete verify.
8. You will have the postmaster dashboard as per below and need to wait for at least 7 days for postmaster generate your domain records.