Sender reputation
The provider's running opinion of your domain and IP, built from how people have reacted to you over time.
Say it out loud
“Gmail's running opinion of us, built over months. One send does not create it, and one bad send can dent it.”
Every mailbox provider scores senders against their own history, at the domain and at the IP. Google retired the colour-coded reputation dashboards in Postmaster Tools, so what you can still read is spam rate, authentication results and delivery errors. Microsoft exposes per-IP data through SNDS. Nobody publishes the model, and the scores sold by third parties are somebody else's guess at it.
Google's stated reason was that reputation was not actionable for most senders. Spam rate always was the number.
iCloud publishes requirements and no telemetry. You infer Apple placement or you do not know it.
Yours
Nobody does this for you.
Where you find it
- Google Postmaster Tools → your domain → Spam Rate
- Microsoft SNDS → your IP range → Data
What goes wrong
Quoting a third-party “sender score” to a client as though it were the provider's opinion. It is a vendor's model of a number Google does not publish, and two vendors will disagree about the same domain on the same day.
What people get told
The claim. “Reputation is attached to our IP, so switching IPs resets it.”
Actually. Domain reputation follows the domain, and at consumer providers it generally matters more than the IP. Moving to a new IP discards whatever goodwill the old one had and starts you at no history, while the domain carries its record with it. It is a way to make a new problem, not to leave an old one.
The dated rules behind this
A definition is not a citation. These are the pages with the primary source, the date it was published, and what to do about it.
See also
Where this sits
Stop 5, reputation decides. Having proved who you are, you find out whether they want you — and that is mostly about your history, not this message.