What Is Sender Score?

Sender Score is a 0-100 reputation rating for email-sending IP addresses, published free by Validity (formerly Return Path) at senderscore.org. The score is calculated on a rolling 30-day window from data observed across Validity's network of mailbox providers and traps, factoring in spam complaint rates, spam trap hits, invalid address attempts, and filtering behavior. Higher is better: scores above 80 indicate a solid reputation, while scores below roughly 70 correlate with meaningful filtering and blocking. Two properties define its practical scope. First, it rates IP addresses, not domains — it says nothing about your domain reputation, which mailbox providers increasingly weight more heavily. Second, most cold email senders use Google Workspace or Microsoft 365, whose messages leave through large shared IP pools managed by the provider; individual senders neither control nor meaningfully influence those IPs' scores, so Sender Score matters mainly to senders operating dedicated IPs.

Sender Score in Practice

In practice, check Sender Score when you control the IP — dedicated SMTP infrastructure, a self-hosted MTA, or an ESP-assigned dedicated IP — and when diagnosing a deliverability collapse where blacklisting is suspected. For the typical cold email operation running Google and Microsoft mailboxes at around 25 emails per mailbox per day, the relevant reputation lives at the domain level, and better instruments exist: Google Postmaster Tools reports domain reputation and spam-rate data for mail sent to Gmail, and inbox placement tests show where messages actually land. The common mistake is treating any single third-party score as ground truth. Teams see a mediocre Sender Score on a shared Google IP and panic, or see a high score and declare deliverability healthy while their domain quietly rots from spam complaints. Reputation is multi-dimensional — IP, domain, content, engagement — and no one number summarizes it; placement tests and reply patterns are the evidence that counts.