Gmail Postmaster Tools, Yahoo Sender Hub, and Microsoft SNDS all publish "reputation" scores. They are all measuring different things, with different weighting, and on different time windows. Here is the practitioner's translation.
Gmail IP reputation. Rolling 7-day window. "High" = under 0.1% complaint rate AND under 0.3% spam-folder rate on engaged senders. "Medium" is your warning. "Low" or "Bad" means you are landing in spam right now.
Gmail domain reputation. Same scale, but tied to your domain not your IP. The trickier one to recover — domain reputation persists across IP changes, so you cannot warm your way out of a damaged domain reputation.
Gmail spam rate. This is the headline number, but it is sampled — only users who actively hit "Report Spam" count, not the algorithmic spam filtering. If your spam rate is 0.0% but you are still landing in spam, that is the algorithm filtering you, not user complaints.
Yahoo CFL. Complaint feedback loop. Reported as a count, not a rate. Yahoo will throttle aggressively at 50+ complaints/day from a single IP regardless of volume.
Microsoft SNDS. Same trip-light system as Gmail, but with extra granularity per /24 IP block. Use it to spot a single bad neighbor in your IP pool.
The shortcut: aim for under 0.05% complaint rate across all three. That single number is the best leading indicator we have found.