# Mastering Email Deliverability with 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
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**Notes:** Data displayed in Google Postmaster Tools is shown with a 48-hour delay.
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## → 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](/guides-and-best-practices/email-deliverability/reputation-and-performance-monitoring/understanding-and-monitoring-the-spam-complaints-rate.md)).
Google-defined spam complaint thresholds:
* **Recommended maximum**: 0.1%
* **Absolute maximum**: 0.3%
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**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.
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## → Feedback Loop
Provides occasional insights into spam complaints if your emails include a Feedback-ID header.
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**Note:** The chart may not always display data. This does not necessarily mean there were no complaints.
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## → 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](https://postmaster.google.com/v2/u/1/spam?h=7)
* [Google article about the Postmaster Tools dashboards](https://support.google.com/a/answer/14668346?hl=fr\&ref_topic=6259779\&sjid=2917677222154997471-EU)
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