Postmaster Tools is a free online tool provided by Google that gives marketers direct access to reputation, deliverability, security, and performance diagnostics directly from Gmail about your email domain and IP.
1. Enter Postmaster Tools - Google Gmail
2. On the bottom right, click Add (plus sign)
3. Enter your authentication domain.
Noted: You can add DKIM (DomainKeys Identified Mail) domains or SPF (Sender Policy Framework) domains.
4. Click Next.
5. Can add TXT data to DNS zone management.
6. To prove that you own this domain, click Verify.
Notes: After verification, it may take some time before your domain verification status is updated to "Verified".
7. Now it shows complete verification.
8. You will have a postmaster dashboard as below and will have to wait at least 7 days for the postmaster to generate your domain record.
