Postmaster Tools the inbox's view of your sending

Why this is different from your own logs

Your own sending logs tell you what left your servers. They don't tell you what Gmail or Outlook did with it. A message can leave cleanly, get accepted at the SMTP layer, and still land in spam. Postmaster Tools is the receiving-end view. It's the closest thing to honest feedback the inbox provides about your sending.

Google Postmaster Tools

The Gmail dashboard, at postmaster.google.com. After domain ownership verification, it surfaces domain and IP reputation as bands (high, medium, low, bad), spam rate over time, SPF/DKIM/DMARC pass rates, delivery error rates, and feedback-loop data. Reputation bands are the headline number most senders watch. A drop from "high" to "medium" is your warning the inbox is starting to filter you. Two notes worth knowing: Postmaster only shows data once you cross a daily volume threshold to Gmail users, and the reputation history is short, so save snapshots if you want to trend.

Microsoft SNDS

The Microsoft equivalent is SNDS (Smart Network Data Services) at sendersupport.olc.protection.outlook.com/snds/. It's older, less polished than the Gmail dashboard, and IP-focused rather than domain-focused. After IP registration and access approval, you see per-IP message counts, spam complaint rates, trap hits, and a reputation rating (Green/Yellow/Red). For senders who care about Outlook/Hotmail delivery, this is the closest thing they publish to "your reputation here." There's also JMRP (Junk Mail Reporting Program), the Outlook feedback loop, which is a separate registration.

What to actually do with the data

Three things, in order. First, watch the reputation indicator. A drop from green to yellow or from "high" to "medium" is your earliest warning that the inbox is filtering more aggressively. Act on it before users start complaining. Second, watch the spam rate. Anything above roughly 0.3% Gmail spam rate is a red flag; above 1% you're in trouble. Third, watch authentication pass rates. If SPF or DKIM pass rates are below 99% you have a config or alignment problem worth chasing, not a reputation one.

How sendmsg.io uses these signals

Postmaster Tools is a slow signal — daily granularity, reputation bands, lag of a day or two. The faster signals (bounces, complaints, block patterns at the SMTP layer) are what the reputation engine watches in real time and uses to adjust sending speed per domain. Postmaster Tools is the slower, ground-truth confirmation. When the engine pulls back on a domain that's about to dip, the dashboard tends to stay green. When sending is healthy, Postmaster confirms it. The two views together are stronger than either alone.

Want to see where your sending stands today before you set up Postmaster? The free deliverability check audits your SPF, DKIM, DMARC, and MX in seconds, no signup.