Mastering Email Deliverability with Google Postmaster Tools

How to Monitor Reputation, Authentication, and Delivery Metrics for Gmail Using Google Postmaster Tools

Google Postmaster Tools is a service by Google designed for email administrators and high-volume senders. It enables senders to monitor the reputation, authentication, and delivery performance of emails sent to Gmail users.

Why Using Google Postmaster Tools?

• Monitor your sender reputation

• Prevent your emails from being marked as spam

• Improve email security (SPF/DKIM/DMARC)

• Identify technical delivery issues

Notes: Data displayed in Google Postmaster Tools is shown with a 48-hour delay.

→ Compliance Status

A high-level dashboard summarizing all key factors that impact deliverability with Google’s email services. This is useful to know what should be improved first.

→ Spam

The spam complaint rate is a critical metric used by Google to evaluate domain reputation. It directly affects your ability to reach recipients' inboxes. Currently, it is the only available way to track spam complaints within Gmail (learn more here).

Google-defined spam complaint thresholds:

• Recommended maximum: 0.1%

• Absolute maximum: 0.3%

Note: A low number of spam complaints combined with a poor sender reputation is not necessarily a positive sign. It may indicate that your emails are not being seen at all — they could be delivered directly to the spam folder — yet they may still cause frustration among recipients.

→ Feedback Loop

Provides occasional insights into spam complaints if your emails include a Feedback-ID header.

Note: The chart may not always display data. This does not necessarily mean there were no complaints.

→ Authentication

Displays results for email authentication protocols:

• SPF

• DKIM

• DMARC

These metrics help verify that your emails are properly configured and protected against phishing and spoofing.

→ Encryption

Monitors whether your emails are transmitted securely using TLS (Transport Layer Security).

→ Delivery error

Tracks the percentage of emails that were rejected or temporarily failed compared to all authenticated traffic.

Useful Links

• Google Postmaster Tools

• Google article about the Postmaster Tools dashboards