OutboxHorizon verifies every address in real time before it leaves your outbox, so you can scale from hundreds to hundreds of thousands of sends without your domain reputation taking the hit.
As your list grows toward the horizon, OutboxHorizon keeps every batch clean, safe, and deliverable.
Real-time SMTP validation holds steady whether you're checking one address or a hundred thousand.
Upload large lists and get a fully segmented, scale-ready report back in minutes.
Filter invalid and risky addresses before volume growth ever puts your domain at risk.
Stop paying to send — and stop burning reputation on — addresses that were never going to land.
Automate verification directly inside high-throughput signup and outreach pipelines.
Track verification trends as your sending volume climbs toward the horizon.
A workflow designed for lists that are only getting bigger.
Drop a CSV of up to 25,000 addresses, paste a single email, or connect the API to your existing signup flow.
Every address is validated at the mail-server level — syntax, domain, mailbox existence, and catch-all detection.
Export a clean list segmented as Valid, Risky, or Invalid, and route only verified contacts into your campaign.
Scale campaign volume with confidence that reputation scales safely alongside it.
Protect shared sending infrastructure as multiple teams ramp up volume.
Automate list hygiene inside high-volume pipelines with a single API call.
Every address is checked at the SMTP mail-server level in real time, delivering up to 99.8% verification accuracy across valid, invalid, risky, and catch-all classifications.
Yes. Upload a CSV of up to 25,000 email addresses at once and get a segmented, downloadable report within minutes.
All verification runs through infrastructure aligned with ISO 27001, SOC 2 Type II, and GDPR standards, and addresses are never sold or shared.
No. New accounts start with 100 free verification credits — no credit card required.
Start free with 100 credits and see how far your reputation can safely scale.