How I Built a 4-Layer Email Validator API with FastAPI and Published it on RapidAPI

I just launched Email Validator API on RapidAPI — a professional email

verification service built with Python and FastAPI.

Most email validators only check syntax. Mine runs 4 layers of verification

and returns a confidence score for every email.

The 4 Layers

Layer 1 — Syntax Check

Validates format against RFC 5322 standards. Also detects common typos

and suggests corrections — for example [email protected] → [email protected].

Layer 2 — DNS / MX Lookup

Confirms the domain exists and is configured to receive emails using

dnspython. Catches domains that look valid but can't receive mail.

Layer 3 — Disposable Domain Detection

Flags throwaway addresses from 3,000+ known providers like Mailinator,

Guerrilla Mail, YOPmail and TempMail. Essential for preventing fake signups.

Layer 4 — SMTP Verification

Performs a real SMTP handshake to confirm the mailbox exists — without

sending a single email. Available on Pro plans.

The Response

Every request returns a detailed JSON breakdown:

{

"email": "

Free plan available — no credit card required.

Happy to answer questions about the implementation!