Mailbox providers judge you on how your last send went. Validating a list before you use it removes the addresses that would have counted against you — and tells you honestly when an address can't be settled.
A hard bounce isn't a failed delivery — it's a signal to the receiving provider that you don't know who's on your list. Enough of those and your good mail starts landing in spam, or nowhere at all.
Providers keep score per sender. Dead addresses in a list you bought a year ago still cost you today.
Some addresses exist only to catch senders who don't clean their lists. One is enough to change how a provider treats you.
Resenty inspects an address without delivering a message to it, so validating a list can't hurt the reputation you're protecting.
Every address comes back as one of four things. Two are decisions; two are honest descriptions of what the mailbox would tell us.
The domain accepts mail and the mailbox exists. Send with confidence.
Keep it. This is the segment you mail.
The mailbox doesn't exist, or the domain can't receive mail at all. Sending here is what produces a hard bounce.
Remove it. Don't hold it for a second attempt later.
The address resolves, but something about it argues against mailing: a disposable domain, a role account like info@, a signal of a complainer or a trap. Reachable isn't the same as worth sending to.
Segment it. Mail cautiously, or leave it out of high-volume sends.
The mail server didn't give us a usable answer — it timed out, throttled the check, or refused to confirm. We say so instead of picking the likelier answer for you.
Nothing — the credit goes back automatically. Re-check later if you like.
A normal mail server will tell you whether a particular mailbox exists. An accept-all — sometimes called catch-all — server answers yes to every address at the domain, whether or not anyone reads it. Companies configure it that way on purpose: to catch typos, to avoid leaking their staff directory, or because a security gateway sits in front of the real mailboxes.
When that's the answer, no verification service can tell the difference from outside. We label the domain accept-all and tell you what that means, rather than dressing a guess up as a verdict.
Two identical answers, one of them certainly wrong. That's the whole reason accept-all exists as a category.
If a mail server won't give us a usable answer, the result comes back as unknown and the credit for that address is returned to your balance automatically — no ticket, no request. A guess that reads like a verdict is worse than no verdict: you'd act on it, and your reputation would pay for it.
Every result carries the reason behind it, so you can see which signal decided the verdict instead of taking our word for it. The accept-all and unknown guide walks through the cases one by one.
Run a sample and read the verdicts yourself — nothing is sent to anyone on it.