- Sender Score, defined
- Sender Score is Validity's free reputation rating for a sending IP address or domain, a quick outside read on how mailbox providers likely view your mail.
Validity runs the lookup at senderscore.org, read on 2026-09-25. You type an IP address or a domain, and the page reports how mailbox providers see you, as a reputable sender or as a spammer. It's free, which is why it's often the first reputation check a new sender runs.
What drives a reputation score is the same behaviour every filter watches. Hard bounces from dead addresses, hits on spam traps, and recipients pressing the spam button all pull sender reputation down. Steady volume to people who open and reply pulls it up.
Check which thing you're scoring. An IP score reflects everything sent from that address, so on a shared IP your number carries other senders' habits too. A domain score follows your brand across IPs and providers, which is why domain reputation matters more once you move between sending platforms.
Watch the trend rather than one reading. A drop after a single campaign usually traces to that send's list: an old export, a bought file, a form with no checks on it. Pull that campaign's bounce report first and look for a cluster of 550 codes.
Pair it with the providers' own tools. Google Postmaster Tools and Microsoft SNDS show what Gmail and Outlook actually record, and a blacklist check shows whether your IP sits on a public blocklist.
Verification protects the part of the score you control before you hit send. Removing dead addresses keeps your bounce rate under 2%, the level mailbox providers treat as healthy. Pristine spam traps look exactly like real mailboxes at the protocol level, so where your list came from still matters as much as how you checked it.
How ZapBounce reports it
ZapBounce guards the inputs behind a reputation score. Dead addresses come back invalid with the server's reply in smtp_code, so you suppress them before the send that would have bounced. Catch-all rows come back as catch_all, apart from valid, so you can pace them in smaller batches, and the disposable flag marks throwaway signups. Every check closes before DATA, so verifying a list sends no mail and never touches your sending IP. Clean a whole file on bulk.
Sender Score: common questions
Is Sender Score free?
Yes. Validity offers the lookup free at senderscore.org for any IP address or domain. You don't need to be a Validity customer to check your own sending infrastructure.
Does Gmail use Sender Score?
Gmail keeps its own reputation data, and Google Postmaster Tools is where you see it. Sender Score is an outside estimate, useful as an early warning, but your Gmail placement follows Gmail's own numbers.
How do I raise my Sender Score?
Cut the behaviour that lowers it. Verify lists before you send so hard bounces stay under 2%, stop mailing people who never engage, and make unsubscribing easy so fewer recipients press the spam button. Scores recover over weeks of clean sending, not after one good campaign.
Does email verification affect my Sender Score?
Only for the better. A verification check closes the connection before any message is sent, so it adds no traffic to your IP. What it changes is your next campaign, which goes out with the dead addresses removed.