SieveCatch bad emails at signup, not in your bounce report.
Two lines of HTML add an inline deliverability badge to any email field: typo rescue, disposable and role detection, and a live MX check, straight from Sieve's validation pipeline.
This input is wired to the exact endpoint the widget calls. Type an address and pause.
Install in 30 seconds
Add data-sieve to your email input and the badge renders right below it. Self-hosting the script elsewhere? Point it home with data-endpoint="https://your-sieve-host" on the script tag. The widget never blocks your form from submitting. It only advises.
What it checks
Syntax
Well-formed address, normalized casing.
Typo rescue
gmial.com → gmail.com with a one-click fix.
Disposable domains
Mailinator, Yopmail and 35+ throwaway providers.
Role addresses
info@, admin@, billing@ flagged as risky.
Mail server (MX)
The domain actually routes mail somewhere.
DNS layer only, by design
The widget never opens an SMTP connection. Live mailbox probing is exclusive to the Sieve app and API, where it's metered and protected.
Honest limits
"Looks deliverable" means the DNS layers passed.
The mailbox itself isn't probed here, and free-mail providers (Gmail, Yahoo, Outlook, iCloud) are never SMTP-probed by Sieve anywhere. For verified mailbox verdicts, run your list through the app or API.
Rate limits keep the free endpoint fast for everyone.
30 checks/minute per visitor and 2,000 checks/day per embedding site; identical addresses are cached for 60 seconds. Past a limit the API returns 429 and the badge simply doesn't render, so signups are never interrupted.
Private by default.
Addresses typed into the widget are checked in memory and never stored, logged, or added to any list.