Updated · 9 min read
Google Postmaster Tools: a walkthrough for people who actually send email
Gmail controls roughly 40% of global inbox share. If your domain reputation with Gmail is bad, nothing else you do matters much — Gmail users won't see your mail. Google Postmaster Tools is Gmail's only public window into how they view your domain. It's free, takes 10 minutes to set up, and most programs never look at it twice. Here's the walkthrough of every tab worth watching and what to do with the data.
Justin Williames
Founder, Orbit · 10+ years in lifecycle marketing
Setup in 10 minutes
Go to postmaster.google.com and sign in with a Google account tied to your domain. Add your sending domain (e.g., marketing.brand.com). Gmail asks you to verify domain ownership via a DNS TXT record — same pattern as Search Console.
Add each subdomain you send from separately. If you send marketing from marketing.brand.com and transactional from accounts.brand.com, they need separate Postmaster entries — reputation is scored per subdomain.
Data starts appearing within 24–48 hours of verification, but you need minimum volume (a few hundred Gmail recipients per day) before charts populate meaningfully. Programs under that threshold will see blank or sparse data, which is information itself — you're not hitting enough Gmail users to matter yet.
Domain Reputation — the one chart that matters
Domain Reputation shows a four-tier rating — Bad, Low, Medium, High — for how Gmail views your domain. This is the single most important chart in Postmaster Tools.
A High domain reputation in Postmaster Tools means inbox placement on Gmail is effectively solved. A Medium rating means it's fine most of the time. Low or Bad means you have a problem visible to 40% of your users.
What to act on:
High → High: No action. Keep doing what you're doing.
Medium → High movement: You're improving. Continue current practices.
High → Medium drift: Investigate recent changes — increased frequency, new audience segment, subject line change that increased unsubscribes. Catch it before it drops further.
Medium → Low drift: Urgent. Reduce volume to engaged users only. Audit the list for dormants.
Low or Bad: Stop sending broad campaigns. Send only to users who opened or clicked in the last 30 days while you diagnose.
The rating is computed on rolling 7-day windows; changes appear gradually. A spike in complaints can drop you from High to Medium within a week.
IP Reputation — less useful than it looks
IP Reputation shows the same Bad/Low/Medium/High scale, but for the sending IP addresses associated with your domain. For senders on a dedicated IP, this tracks closely with your domain reputation. For senders on shared IPs (most smaller programs), the IP reputation reflects the pool — your neighbours' behaviour.
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In 2026, Gmail's filtering weights domain reputation more heavily than IP reputation. IP reputation is worth monitoring but secondary.
Spam Rate — your complaint rate on Gmail specifically
Spam Rate shows the percentage of your Gmail-delivered mail that users marked as spam. This is the signal Gmail uses most directly to degrade your reputation.
Healthy: below 0.1%. No concern.
Warning: 0.1–0.3%. Gmail is starting to treat you as spam-adjacent. Investigate the root cause — frequency, unsubscribe flow, or dormant audience.
Emergency: above 0.3%. Gmail will increasingly place your mail in the spam folder or block it. Cut volume immediately to the most engaged 20% of your list and investigate. Recovery is 6–12 weeks once the rate comes back down.
The spam complaints playbook covers the four levers that reduce complaint rate. Use Postmaster's Spam Rate as the canonical measure when assessing Gmail-specific complaints.
Authentication — the chart that should always be green
The Authentication tab shows SPF, DKIM, and DMARC pass rates for your Gmail-delivered mail.
All three should be at or near 100%. If SPF drops, check that your ESP's sending servers are included in your SPF record. If DKIM drops, check that DKIM signing is enabled in your ESP and the selector is published correctly in DNS. If DMARC drops, check your DMARC policy and alignment.
Any rate below 95% means authenticated mail is failing a check somewhere — typically a configuration issue that's easy to fix once identified. The SPF/DKIM/DMARC explainer covers each in depth.
Delivery Errors — where things are being rejected
The Delivery Errors tab shows the percentage of your mail that Gmail outright refused (bounced at the SMTP level), broken down by reason. Common categories: "sender IP reputation", "policy-related", "content-related", "too-many-recipients".
In healthy programs this chart is near-empty — Gmail accepts most mail and filters at the inbox/spam-folder level rather than rejecting at SMTP. A spike in "sender IP reputation" rejections means your IP reputation has dropped below Gmail's acceptance threshold. A spike in "policy-related" means your content is tripping specific filter rules (often an image-to-text ratio issue or URL shortener flagging).
How often to check
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Most programs benefit from screenshotting the Domain Reputation chart weekly and keeping the images in a shared drive. You want to see the trend, not just the current state. A "High" that just dropped from a consistent 60 days of "High" is a different signal from a "High" that just climbed from "Medium".
The Deliverability Management skill includes Postmaster Tools monitoring as part of its weekly cadence.
Frequently asked questions
- What's the minimum volume I need for Postmaster Tools to show useful data?
- A few hundred Gmail recipients per day, sustained. Below that, the charts will be sparse or blank. If you're not seeing data despite verified setup, your Gmail volume is below Google's threshold for reporting — in which case, you likely don't have a Gmail-specific deliverability problem worth worrying about yet.
- My domain reputation is 'Medium' — is that bad?
- Medium is fine. It means Gmail delivers most of your mail to the inbox but applies some additional scrutiny on borderline cases. High is better but not essential for healthy delivery. Act only if you're trending downward (Medium → Low) or if Medium has persisted for months without any upward movement — that suggests engagement or complaint issues worth investigating.
- Why does Postmaster not show individual complaints?
- Gmail is the only major ISP that doesn't provide a feedback loop (FBL) for individual complaints. They show the aggregate spam rate but don't tell you which users complained. Your ESP's FBL data covers the other major ISPs (Yahoo, Microsoft, AOL, Comcast); Gmail complaints are visible only as a rate.
- Should I have separate Postmaster entries for each subdomain?
- Yes. Gmail scores reputation at the subdomain level, so marketing.brand.com and accounts.brand.com have independent reputations. Add each as a separate Postmaster domain; you'll see different reputation ratings for each, which is the point.
- My spam rate just jumped from 0.1% to 0.4% — what do I do?
- Stop sending broadly. Send only to users who engaged (opened or clicked) in the last 30 days. Investigate what changed — new audience segment, frequency increase, a specific campaign that over-indexed on complaints. Correct the root cause before resuming broad sending. Recovery takes 6–12 weeks.
- IP reputation low but domain reputation fine — what does that mean?
- You're on a shared IP and your neighbours are dragging the IP pool down. Your domain-level behaviour is healthy; the IP problem isn't yours to fix. Either tolerate it (domain reputation is the heavier weight in modern Gmail filtering) or graduate to a dedicated IP if volume justifies it.
- Should I share Postmaster Tools access with my whole team?
- At least two people — the CRM/lifecycle lead and someone from engineering or devops. Access is via Google Workspace accounts, not shared credentials. Verify that the handoff is documented; a Postmaster Tools lapse (forgotten login, no monitoring) is how reputation drifts without anyone noticing.
This guide is backed by an Orbit skill
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