Email Signup Validation n8n Workflow: DNS & Data Table

Validate signup emails with real DNS + registration signals (and log every check)

This n8n workflow exposes a webhook that evaluates an email address during signup using Cloudflare DNS-over-HTTPS lookups, RDAP domain data from rdap.org, and a disposable-domain blocklist from GitHub—then returns an accept / review / reject verdict with reasons and saves the result to an n8n Data Table.

What this workflow does

• Receives a POST webhook containing an email address (JSON body, form fields, or query parameter) and normalizes it for consistent checks.
• Performs DNS-over-HTTPS checks via Cloudflare: retrieves MX, A, DMARC (TXT), and SPF (TXT) records.
• Fetches RDAP registration/expiry data from rdap.org to help infer domain age and registration status signals.
• Downloads a disposable-email domain blocklist from GitHub and flags disposable domains.
• Interprets DNS/RDAP outcomes to detect conditions such as NXDOMAIN, null MX (RFC 7505), mail-to-A fallback, mail provider hints, and domain age.
• Generates typo suggestions for common mistyped domains (e.g., gmial.com → gmail.com) using an edit-distance approach.
• Checks prior activity by counting how many times the canonicalized address was checked using the n8n Data Table, then combines this with role-address and policy checks.
• Returns a JSON response with verdict, reasons, key signals, and inserts a log row into the Data Table.

Use cases

• SaaS signup throttling: reduce fake accounts by rejecting disposable or non-routable domains.
• Risk-based onboarding: send suspicious emails to a “review” queue instead of hard-blocking.
• Data-driven fraud prevention: keep an audit trail of validation outcomes in an n8n Data Table.

Technical details

• Webhook endpoint (POST) for email validation requests.
• Cloudflare DNS-over-HTTPS for MX, A, DMARC (TXT), SPF (TXT).
• rdap.org RDAP lookups for domain registration/expiry signals.
• GitHub source for disposable-domain blocklist.
• n8n nodes: set, code, merge, webhook, data table, and sticky note.

Data Table setup: create an n8n Data Table named email_checks with columns address_key, email, domain, verdict, reasons, and checked_on.