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Sender requirements & Postmaster Tools FAQ

Postmaster Tools helps email senders analyze email performance and deliver messages to the right place. With Postmaster Tools, you have access to data and diagnostics about your email, including delivery errors, spam reports, and feedback loops. 

To help bulk email senders meet the requirements in our Email sender guidelines, we've added a new Compliance status dashboard to Postmaster Tools. This dashboard is available only to bulk senders.

Email sender guidelines & Postmaster Tools

We recommend email senders use Postmaster Tools to make sure they’re meeting the requirements in Gmail’s Email sender guidelines

To learn more about Postmaster Tools, visit Get Started with Postmaster Tools. You can also sign in to Postmaster Tools.

Postmaster Tools dashboards for email senders

These Postmaster Tools dashboards provide detailed information about your email delivery and message format:

SPF and DKIM authentication

The Postmaster Tools Authentication dashboard provides detailed information about SPF and DKIM authentication. If your organization uses more than one domain and uses more than one DKIM key or SPF record, this dashboard might show no authentication for your domains that don’t send email.

For example, you might have 2 domains, and, and have email authentication (DKIM and SPF) set up for both. However, if you only use to send email, Postmaster Tools might show no authentication results for

To learn more about SPF and DKIM, visit Prevent spam, spoofing & phishing with Gmail authentication.

DMARC authentication

To check the details of your DMARC authentication, use a third-party DMARC authentication tool from the internet. We recommend you always set up DMARC authentication for your domain. Your DMARC policy can be set to minimal enforcement, using a policy that’s set to none (p=none) and applied to 0% of your messages (pct=0). 

To learn more about setting up DMARC, visit Help prevent spoofing and spam with DMARC.

Message format

To review information and errors about email message format, check the "Delivery errors" dashboard in Postmaster Tools. To correct message formatting issues, check message rejection errors that mention bad format, for example 550 5.7.1 errors. For more information about error codes, visit Gmail SMTP errors and codes.

DNS records

To verify your domain's DNS A and PTR records, use a third-party DNS record tool from the internet. To learn more about DNS records, visit Resource record types.


To review how much of your email traffic is encrypted, check the "Encryption" dashboard in Postmaster Tools. Percentage values for Inbound and Outbound TLS are displayed at the bottom of the dashboard.

User-reported spam rate

To monitor your email spam rate, check the "Spam Rate" dashboard in Postmaster Tools. Values for user-reported spam are displayed at the bottom of the dashboard.

Unsubscribe issues

To monitor your messages or campaigns for a high volume of complaints from recipients, add the Feedback-ID: header to your messages, and use Feedback Loop. For details, visit Feedback Loop.

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