Most founders don't realize how polluted their signup funnel is.

Here's what disposable email addresses actually cost you:

Inflated metrics. Your "10,000 users" includes thousands of throwaway accounts that will never convert. You're making product decisions based on junk data.

Wasted free tier. Burner accounts farm your free quota. Every abuse check you hand out is money left on the table.

Broken email deliverability. Sending to temp inboxes tanks your sender reputation — hurting even your real users.

The fix is one API call at signup:

GET /v1/check?email=user@example.com
→ { "is_temp": true, "score": 0.97, "reason": "known_disposable" }

Block if is_temp is true. Use the score field to soft-block borderline cases. That's it.

TempShield covers 2,800+ disposable domains, responds in under 30ms, and refreshes its blocklist every 24 hours. Free tier is 1,000 checks/month — no credit card required.

If you're running a SaaS without email validation at signup, you're flying blind.