Sender Score: the 0-100 reputation rating for sending IPs
Sender Score is a number from 0 to 100 that Validity (formerly Return Path) assigns to every sending IP address. It is recalculated on a rolling 30-day window, so it reflects what you have been doing lately, not what you did two years ago.
How the score is calculated
Validity pulls data from its network of mailbox providers across billions of processed messages. The formula is proprietary, but the inputs are documented. Complaint rate carries the most weight: the percentage of recipients who marked your message as spam. After that come unknown user rate (mail sent to addresses that do not exist), spam trap hits, infrastructure signals (PTR records, rDNS, SPF/DKIM authentication), and blocklist presence on Spamhaus, Barracuda, or SORBS.
The 30-day window cuts both ways. A cleanup effort takes 2-4 weeks to show up in the score. One bad mailing can pull it down fast and keep it there for a month even after the problem is fixed.
Reading the tiers
80-100: good reputation. Most messages reach the inbox. Providers trust the IP. This is the target zone.
70-79: average reputation. Messages generally deliver, but some land in spam. Check which factor is pulling the score down before the next send.
Below 70: poor reputation. A significant share of messages gets filtered. Some providers may block the IP entirely. Serious remediation is required.
What Sender Score does not measure
Sender Score measures the IP, not the domain. If you send through a shared IP pool (standard with most ESPs), the score reflects the entire pool's behavior, not just yours. In that situation the number tells you less than you might expect.
Gmail, Yandex, and Mail.ru run their own internal reputation systems. A Sender Score of 90 from Validity does not mean Google Postmaster Tools will show a High reputation for your domain. These are separate systems with separate data. Use Sender Score alongside GPT data and your ESP delivery logs, not instead of them.
How to check your score
Go to senderscore.org, enter your sending IP, and you will get the result immediately. Detailed breakdowns require a free account. If you do not know your sending IP, pull the headers from any outgoing message and look at the Received field, or ask your ESP directly.
uChecker reduces bounce rate and helps keep Sender Score in the healthy range. A clean list free of invalid addresses and spam traps is one of the strongest factors behind a good rating.
How the number is built
Sender Score is calculated by Validity from data across a large panel of receiving servers. The inputs are the ones providers themselves weigh: complaint rate, hits on spam traps, volume consistency, bounce rate, and whether the IP appears on public blocklists.
It is a rolling thirty-day figure, so a single bad campaign drags it down for a month rather than a day. That lag cuts both ways — recovery also takes weeks of clean sending, not one good send.
What it does not tell you
The score belongs to an IP address, not to your domain or your content. On a shared pool it reflects everyone sending through it, so a good score there says little about your own practice. And no provider takes it as input: Gmail and Yandex run their own reputation systems and have never used Sender Score.
Treat it as a thermometer rather than a verdict. A drop is a reliable signal that something changed in your sending; the absolute number matters much less than its direction.