Captchainbox
Start free
Stop AI cold spam · Gmail only

The CAPTCHA for your inbox.

Stop AI spam from flooding your inbox and calendar. Known contacts get through instantly. Everyone else proves they're human first.

Start with GmailSee how it works

7-day free trial · 5-minute setup · Archived, never deleted

Mail
Live
InboxArchived 2Trusted 284
SC

Sarah Chen

now

sarah@designco.com

Re: new design direction

Checking sender…Delivered to your inbox

Built for inboxes overwhelmed by AI outreach

AI cold outreach is nearly free. Real messages get buried.

Spam filters catch the obvious, but plausible outreach slips through — and calendar invites bypass filters entirely. You miss what matters and drown in what you didn't ask for. We give you back the front door of your inbox.

Step 01

Connect Gmail. Once.

Sign in with Google. Captchainbox scans your sent history and whitelists everyone you've written to. No one you know gets blocked. Under five minutes.

  • Sent-history import
  • Curated transactional domains
  • No re-onboarding needed
See connection details

Gmail connected

you@gmail.com

Scanning sent history…0%

Analyzed

2,847

Trusted

284

Status

Active

Step 02

Every email, silently checked.

New email arrives. Captchainbox checks the sender instantly. Known contacts reach your inbox. Unknown senders are archived (never deleted) and sent a CAPTCHA link. Calendar invites from unknowns are auto-declined.

  • Sender-only filtering — never content
  • Archived, never deleted
  • Calendar protection included
See filter rules
Inbox protection
Live

Step 03

Real people pass in 30 seconds.

Unknown senders get a simple CAPTCHA. Complete it and their message is delivered immediately — trusted for 3 days, no re-verification for follow-ups.

  • One-tap CAPTCHA
  • 3-day grace window
  • Branded verification page
See verification flow
captchainbox.com/verify/···

Inbox verification

Complete this quick check to prove you're human and get your message delivered.

Inbox verification

I am human
Deliver my message

You're verified

Your message is on its way to their inbox.

Pricing

One plan. Everything included.

Free 7-day trial, no credit card required.

Per inbox

$5/ month

7-day free trial included

  • Real-time inbox filtering
  • Calendar invite protection
  • Trusted circle from sent history
  • Introduction detection via CC
  • Configurable filter rules
  • Custom auto-reply templates
  • Emails archived, never deleted
Start free trial

Take back your inbox.

Set up in 5 minutes. Free to get started.

Start with Gmail

Curious what senders see? Send me an email and see the verification flow yourself.