8 min read
Real-time email feedback in a React signup form
Check signup emails on blur in React 19: catch typos, disposable domains and role addresses with clear messages, a backend proxy and no blocking on failures.
Tutorials
Copy-paste integrations for Node, Python, Next.js, Workers, Supabase, Auth0, Sheets and more.
- 7 min read
Classifying new signups with n8n
Build an n8n workflow that classifies each new signup's email as company, webmail, disposable or role-based and routes it, plus a deduped nightly batch.
- 7 min read
Enriching HubSpot contacts with a workflow webhook
Use a HubSpot workflow's Send a webhook action to classify each new contact's email domain and write category, spam verdict and company fields to the record.
- 6 min read
Cleaning an email list from a CSV with a short script
A dependency-free Python script that dedupes a CSV of emails, classifies each domain, drops disposable and invalid addresses, and respects API rate limits.
- 7 min read
Classifying a list of emails in Google Sheets
An Apps Script that tags every email in a Google Sheet as company, free, disposable, ISP or education, with throttling, domain dedupe and a safely stored key.
- 6 min read
Checking emails in an Auth0 pre-user-registration Action
Reject disposable and machine-generated signup emails in an Auth0 pre-user-registration Action, with secrets, a timeout, 429 backoff and fail-open logic.
- 7 min read
Blocking disposable emails in Supabase Auth
Use Supabase's Before User Created hook and an Edge Function to reject disposable and machine-generated emails at signup, with timeouts and fail-open handling.
- 7 min read
Email validation at the edge with Cloudflare Workers
Screen signup emails in a Cloudflare Worker before they reach your origin: secrets, timeouts, 429 backoff and fail-open forwarding, with complete code.
- 7 min read
Validating signup emails in a Next.js server action
Check signup emails for disposable and machine-generated addresses inside a Next.js server action, with timeouts, 429 backoff and a clear fail-open policy.
- 6 min read
Checking emails in the Auth.js (NextAuth) signIn callback
Use the Auth.js v5 signIn callback to block disposable and machine-generated emails for magic-link and OAuth sign-ins, with caching and fail-open handling.
- 6 min read
Domain lookup API quickstart: curl, JavaScript, Python, Go
Call the pingutil domain lookup API from curl, JavaScript, Python and Go, with timeouts, 429 handling and the fields you should actually read.
- 6 min read
Blocking disposable emails with Firebase Auth blocking functions
Reject disposable and machine-generated emails in Firebase Auth with a beforeUserCreated blocking function: setup requirements, full code, timeouts and fail-open.
- 8 min read
Email domain checks in Go
A Go signup check with net/http, context timeouts, typed structs, an ICANN-only eTLD+1 helper built on x/net/publicsuffix, a TTL cache and fail-open 429 handling.
- 5 min read
Validating email domains in Ruby on Rails
A Rails EachValidator that rejects disposable, machine-generated and optional free webmail emails, with Net::HTTP timeouts, Rails.cache and fail-open logic.
- 6 min read
Laravel validation rule for disposable and personal emails
A Laravel ValidationRule that rejects disposable, machine-generated and (optionally) free webmail addresses, using the Http facade with timeouts, retry and caching.
- 6 min read
Stopping fake WordPress registrations with an email check
Block disposable and machine-generated emails at WordPress and WooCommerce registration with the registration_errors filter, a short timeout and fail-open logic.
- 7 min read
Giving an AI agent an email and domain lookup tool
Tool definitions for Anthropic tool use, OpenAI function calling and MCP that let an LLM agent classify emails and domains with a real API, key kept server-side.