Sender Score is a reputation rating from 0 to 100 for a sending IP address, published by Validity, the company that took over Return Path. It is calculated from data Validity collects across a network of mailbox providers and filtering companies, looking at factors such as complaints, volume, spam-trap hits and unknown users over a rolling period of around 30 days.
The score is a convenient shorthand. Higher is better: many people treat scores above about 80 as good and scores below about 70 as a sign of problems, though Validity itself presents the score as a guide rather than a pass mark. You can look up any IP for free on the Sender Score website after registering.
Its limits are important. Sender Score rates IP addresses, not domains, while today’s mailbox providers lean heavily on domain reputation. It draws on Validity’s own data network, and Gmail, Outlook and Yahoo each use their own internal systems that you can’t see. A good Sender Score doesn’t guarantee inbox placement at Gmail, and a middling score on a shared IP may say more about other senders than about you.
Use Sender Score as one input among several. It is most meaningful if you have a dedicated IP, where the score reflects only your sending. For shared IPs, focus on your domain’s metrics: Google Postmaster Tools, your complaint and bounce rates, and engagement by provider.
A Chennai insurance broker with a dedicated IP sees its Sender Score fall from 92 to 74 over two weeks. Checking its own data, it finds a spike in unknown-user bounces from a newly imported agent list. It suppresses the bad addresses, verifies the rest, and the score recovers over the following month.