Stop sending to addresses that don't exist.
Every email address is validated automatically when you import leads. Sendbox categorizes each address as deliverable, undeliverable, risky, or unknown with confidence scores so you can decide what makes the cut.
Lambda Group
Bad addresses caught on import.
No separate step required. Validation runs automatically the moment leads enter your system.
Deliverable, undeliverable, risky, and unknown, far more useful than a simple pass or fail.
Every address carries a confidence score, letting you decide how aggressive your filtering should be.
Domains that accept everything get flagged, so you know which validation results to trust less.
Validation baked into every import.
Upload a CSV or add leads by hand, and Sendbox validates every address automatically as part of the import itself. There's no separate step to remember to run.
Syntax checks catch formatting mistakes, domain and MX record checks confirm the domain can actually receive mail, and mailbox-level verification checks whether the specific address exists. Catch-all detection flags domains that accept everything.
Every address lands in one of four categories, deliverable, undeliverable, risky, or unknown, each with a confidence score you can use to set your own threshold for what gets into your campaigns.
Bought a list from a data provider? Validation reveals the real quality of what you paid for. A high share of undeliverable addresses tells you the data was bad.
Some domains accept mail to any address, which makes verifying individual mailboxes tricky. Sendbox flags catch-all domains so you can decide how to handle them.
ESPs start penalizing you once bounce rates exceed 2%. Validation keeps you under that line by filtering bad addresses out before they ever bounce.
Four categories, not just pass or fail.
Validation that runs automatically, not a step your team forgets
Most platforms treat validation as a separate action someone has to remember to click, and they often don't. Sendbox validates during import instead, so by the time leads land in the system, the bad addresses are already flagged and campaigns start clean by default.
Four categories, not just pass or fail
Binary validation misses the nuance: an address can be technically valid yet still risky. Sendbox sorts every address into one of four buckets, deliverable (safe to send), undeliverable (don't send), risky (proceed carefully), or unknown (couldn't determine status), each carrying a confidence score so you can draw your own line on risk.
Catch-all detection prevents false positives
Some domains accept mail sent to any address, even ones that don't actually exist, and standard validation marks these as "valid" simply because the server accepted the connection. Sendbox specifically detects catch-all domains and flags them, so you know to trust that particular result a little less.
Got questions? We've got answers.
Still stuck? Talk to us →Syntax correctness, domain validity through MX records, and whether the mailbox itself exists, plus detection of catch-all domains that accept mail to any address. Every email lands in a deliverable, undeliverable, risky, or unknown category with a confidence score.
Related pages
More Testing
Explore Sendbox
Compare & decide
Ready to land in primary?
Get your own isolated Sendbox setup running and start sending inside 15 minutes.
Every plan includes a dedicated IP. Cancel whenever you want.