Gmail Postmaster Tools API
Gmail Postmaster Tools API
Gmail Postmaster Tools API queries Gmail delivery quality for sender domains — spam rate, authentication (SPF/DKIM/DMARC) pass rate, reputation score.
Direct delivery data from Gmail
Only Gmail data (no Outlook, Yahoo, etc.)
Verify domain ownership at postmaster.google.com to enable the API. GET /v1/domains/{domain}/trafficStats to fetch delivery stats.
Uptime · 30-day window
About this API
Postmaster Tools is Google's tool for senders — any company sending large volumes of email to Gmail users (SaaS transactional notifications, newsletter platforms, marketing email vendors) should use this. The API provides four core data types: spam rate (how many emails were classified as spam), IP reputation (your sending IP's reputation in Gmail's eyes), domain reputation (domain reputation), SPF/DKIM/DMARC pass rate (how many emails passed authentication). This data is the foundation for diagnosing delivery issues — if spam rate spikes, you need to quickly check email content, arrival patterns, user engagement, etc., or your domain gets downgraded to Gmail's spam folder. More authoritative than the "fuzzy metrics" of SendGrid and other ESPs because it comes from Gmail itself.
What you can build
- 1Bulk email senders monitor Gmail delivery quality
- 2Investigate why emails are classified as spam
- 3Combined with SendGrid/Mailgun to optimize deliverability
- 4Trigger alerts on abnormal spam rate
Strengths & limitations
Strengths
- Direct delivery data from Gmail
- Distinguishes user-marked-spam vs filter-classified-spam
- Free
Limitations
- Only Gmail data (no Outlook, Yahoo, etc.)
- Data has 1-2 day update lag
- Sparse data for low-volume senders — trends not visible
Example request
curl https://google.com/<endpoint>Getting started
Verify domain ownership at postmaster.google.com to enable the API. GET /v1/domains/{domain}/trafficStats to fetch delivery stats.
FAQ
How do I know if my domain reputation is affected?+
A spamRate > 0.1% over time is high; a reputationCategory of LOW or BAD requires immediate investigation.
Can I see which specific emails were marked as spam?+
No. Postmaster Tools only provides aggregated stats. Per-email diagnosis requires ESP logs or test-account inspection.
Technical details
- Auth type
- unknown
- Pricing
- unknown
- Protocols
- REST
- SDKs
- python, javascript, go, java
- Response time
- 41 ms
- Last health check
- 5/12/2026, 7:37:31 AM
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