Tutorials8 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.
Blog
Guides for developers and growth teams on signup fraud, disposable email, telling business from personal addresses, and enriching leads from a domain.
- Tutorials7 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.
- Email validation6 min read
Cleaning a newsletter list before you hit send
What to remove from a newsletter list before a send: disposable and dead domains, provider typos, system addresses and sometimes role addresses. With a script.
- Tutorials7 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.
- Disposable email6 min read
Card testing and fake accounts: where email signals help and where they don't
Card testing is stopped mainly by payment-side controls: rate limits, CAPTCHA, Radar-style rules and 3DS. Email signals help with the fake accounts around it.
- Tutorials6 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.
- Company enrichment6 min read
Free domain intelligence API: what you can get without paying
What a free domain intelligence API should return, exactly what pingutil gives for free (fields and rate limits), what it doesn't do, and how free tiers compare.
- Tutorials7 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.
- Disposable email7 min read
Keeping fake and internal signups out of product analytics
Tag every signup as real, suspect, fake or internal when the account is created, then filter on that tag in PostHog, Mixpanel, Amplitude or plain SQL.
- Tutorials6 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.
- Business email7 min read
Personalizing onboarding from the signup email domain
Branch onboarding on the signup email domain: team setup for company addresses, a solo flow for Gmail, an education plan for .edu. Code, UX copy and privacy rules.
- Tutorials7 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.
- Company enrichment8 min read
A B2B lead scoring model built from email and company data
A transparent points-based lead scoring model from email category, company size, industry and email signals, with starting weights and a calibration method.
- Tutorials7 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.
- Company enrichment8 min read
Filtering fake leads from website forms with a webhook
Put a small webhook between Tally or Typeform and your CRM: verify the signature, classify the submitter's email, and route real leads to the CRM and junk to review.
- Tutorials7 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.
- Tutorials6 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.
- Tutorials6 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.
- Tutorials6 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.
- Email validation7 min read
Building a simple email risk score from free signals
A practical email risk score for signups: which free signals to use, hard rules vs points, score bands, and how to calibrate it against your own abuse data.
- Tutorials8 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.
- Email validation6 min read
Signup domains with no website: what it tells you
A signup domain that receives mail but has no website is a useful fraud signal, not a verdict. What DNS shows, the innocent cases, and how to score it.
- Tutorials5 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.
- Email validation5 min read
Catch-all email domains and what they mean for validation
A catch-all domain accepts mail for any address, so verifiers can't confirm a mailbox. How detection works, why it's common in B2B, and how to treat it.
- Tutorials6 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.
- Email validation6 min read
Gmail dots, plus addressing and duplicate accounts
Why jane.doe+trial2@gmail.com and janedoe@googlemail.com are one inbox, and how to build a canonical email key that catches duplicates without breaking login.
- Tutorials6 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.
- Email validation7 min read
SMTP mailbox verification: why it's unreliable
What an SMTP mailbox probe really tests, the six ways its answers mislead you (VRFY, catch-all, greylisting, port 25 blocks), and what to use instead.
- Business email4 min read
Is a Gmail address a business email?
No: @gmail.com is free personal webmail, even when a business uses it. Google Workspace on a custom domain is business. How to tell them apart in code.
- Email validation6 min read
Internationalized email domains: punycode and normalization
Handle addresses like jane@bücher.de: convert the domain to punycode with UTS 46, leave the local part alone, and avoid the traps that split one domain in two.
- Disposable email5 min read
How to check if an email address is disposable (with and without code)
Check if an email is disposable by hand (public blocklist, MX lookup, a quick search) or in code with a list or an API. Includes a short checklist.
- Email validation7 min read
DNS-over-HTTPS for domain checks in serverless code
Run MX, A and AAAA lookups from edge functions and serverless runtimes with the Cloudflare and Google DoH JSON APIs: request format, status codes and gotchas.
- Business email7 min read
Email and domain intelligence glossary
Plain definitions of 40 email and domain intelligence terms, from catch-all and null MX to eTLD+1, RDAP, SPF and DMARC, with links to deeper guides.
- Email validation6 min read
Checking MX records to see if a domain can receive email
How to tell from DNS whether a domain accepts mail: MX lookups, the implicit MX fallback, null MX, and which DNS errors should never block a signup.
- Company enrichment7 min read
LLM lead qualification: where a lookup API beats the model
Which lead qualification steps an LLM is good at, which ones a deterministic lookup should own, and a pipeline that puts each in the right place.
- Email validation6 min read
Why an email regex is never enough
A regex can only tell you an email address is shaped right. What to match, what to deliberately reject, and the checks a pattern can never replace.
- Tutorials7 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.
- Email validation6 min read
Email validation vs verification: what each one catches
Validation checks that an address could work. Verification proves someone receives mail there. What each layer catches, misses, and where it belongs.
- Email validation7 min read
What SPF and DMARC records tell you about a signup domain
SPF and DMARC show whether a domain's owner set up outbound mail authentication. How to look them up over DNS, what they prove, and what they don't.
- Company enrichment6 min read
Spotting multiple signups from the same company
Detect teammates who sign up separately: group signups by registrable domain, skip webmail and schools, then send a team invite or a sales alert.
- Disposable email7 min read
Domain age as a signup risk signal
How to check a signup domain's registration age with RDAP, when a young domain means risk, the innocent cases, and how to combine it with a domain lookup.
- Company enrichment6 min read
eTLD+1 explained: why mail.stripe.com is stripe.com
What eTLD+1 means, how the Public Suffix List defines it, why splitting on dots breaks on bbc.co.uk, and how to compute it in JavaScript, Python and Go.
- Email validation6 min read
RDAP vs WHOIS: looking up domain registration data
RDAP replaced WHOIS for generic TLDs in 2025. How the two protocols differ, how to query RDAP in code, and where you still need WHOIS for country-code domains.
- Company enrichment7 min read
Caching domain lookups: keys, TTLs and when to refresh
How to cache email and domain lookup results: what to key on, which fields can share a cache entry, TTLs per data type, stale-on-error, and when to force a refresh.
- Email validation6 min read
Email verification services vs domain classification APIs: which do you need?
Verification services check if a mailbox will accept mail. Classification APIs tell you what kind of address it is. Which job needs which, and when to use both.
- Company enrichment7 min read
How accurate is LLM-based company enrichment?
Where AI company enrichment is reliable, where it fails (invented funding, stale HQs, the wrong company), and the guardrails that make it safe to use.
- Company enrichment6 min read
Free domain lookup tools: WHOIS, DNS, classification and company data
Free domain lookup tools grouped by the question they answer: registration (RDAP, WHOIS), DNS, domain type and company data, with commands you can run now.
- Company enrichment6 min read
CRM data hygiene: cleaning contacts by email domain
Clean up a CRM by email domain: normalize company domains, merge duplicate accounts, separate personal and disposable contacts, and keep it clean.
- Disposable email6 min read
Free tools for detecting disposable email addresses
Free disposable email detection tools by type: open lists, libraries, keyless endpoints, free APIs and web checkers, with list sizes and the trade-offs of each.
- Company enrichment8 min read
Routing inbound leads by company size and industry
Build lead routing rules on enriched company size, industry and country: segment buckets, an ordered rule table, confidence gates and a triage queue for unknowns.
- Email validation6 min read
Free email validation APIs compared (and what "free" really includes)
Free tiers of ZeroBounce, Abstract, Hunter, MailboxValidator, Emailable, Kickbox and pingutil compared: quotas, resets, SMTP checks and where each fits.
- Company enrichment6 min read
Enriching inbound leads from nothing but an email domain
Design a lead enrichment step that starts from a work email: gate by domain type, enrich async, record provenance, never overwrite human input.
- Company enrichment7 min read
Clearbit alternatives after the HubSpot acquisition
What changed at Clearbit after HubSpot bought it, which features are gone, and a replacement for each one: logos, enrichment, form shortening and signup screening.
- Company enrichment7 min read
Free company enrichment APIs: what you actually get
Free company enrichment comes in three forms: capped tiers of paid databases, LLM-generated profiles, and DIY scraping. What each returns, and how to test them.
- Company enrichment6 min read
What is domain intelligence? A practical definition
Domain intelligence is everything you can learn about a domain name: what kind of domain it is, whether it works, who registered it and which company is behind it.
- Business email6 min read
Detecting government email domains in every country
A country-by-country guide to government email domains: what .gov, gov.uk and gouv.fr rules catch, what they miss (gc.ca, bund.de, go.jp), with detection code.
- Business email6 min read
Verifying student and academic email addresses worldwide
How to check if an email belongs to a university or school: TLD rules that work, the countries they miss, a university domain list, and a verification flow.
- Business email6 min read
ISP email domains: why comcast.net is not a company
comcast.net, btinternet.com and orange.fr are consumer ISP mailboxes. Why they break lead enrichment and routing, which domains to list, and how to treat them.
- Business email6 min read
Role-based email addresses (info@, sales@): what to do with them
Role-based addresses like info@ and support@ are shared inboxes, not people. When to accept, flag or reject them, and how to detect them without false hits.
- Business email7 min read
How to find the company behind an email address
Turn an email address into a company name: normalize the domain, discard webmail and ISP domains, then resolve the rest from its website or an enrichment API.
- Business email6 min read
Should your B2B signup form require a work email?
When a work-email-only signup helps a B2B funnel, when it quietly costs you customers, and how to ask for a work email without rejecting anyone.
- Business email5 min read
Free email provider domains: the list that actually matters
The webmail domains worth listing, grouped by provider and region, why 30,000-domain lists answer a different question, and how to tune a list to your users.
- Business email6 min read
How to tell a business email from a personal one in code
Classify an email as business or personal: reduce to the registrable domain, check provider lists, then use MX records to catch personal custom domains.
- Disposable email6 min read
Should you block disposable emails or just flag them?
A decision framework for disposable email at signup: which surfaces deserve a hard block, when to flag instead, and what a flag should do to the account.
- Disposable email7 min read
Disposable email checker APIs: open lists vs paid services
Open blocklists, free hosted endpoints, paid verification APIs and domain intelligence APIs compared on cost, latency, freshness and failure modes.
- Disposable email6 min read
Referral and promo-code abuse: the email signals that help
Referral abuse is one person posing as many. The email signals that link those fake referees together, with code that scores a referrer before you pay out.
- Disposable email7 min read
Detecting machine-generated email addresses
How to spot bot-made addresses like xk7qmz2p@gmail.com from the local part alone: the features that work, a runnable scorer, and where it flags real people.
- Disposable email6 min read
Apple Hide My Email, Firefox Relay and SimpleLogin are not disposable email
Relay addresses look random but forward to a real, long-lived inbox. Why they differ from disposable email, why filters misfire on them, and how to allow them.
- Disposable email7 min read
Fake signups: where they come from and how to filter them
Fake SaaS signups come from five different sources, and each needs a different filter. How to tell which one you have, and what to put in front of each.
- Disposable email7 min read
Stopping free-trial abuse without punishing real users
A practical playbook for SaaS founders: screen signup emails, dedupe identities and gate trial value in steps, so abusers stall and real users never notice.
- Disposable email7 min read
Why disposable email blocklists go stale, and how to keep yours fresh
The open disposable domain list doubled in a year. Why vendored copies decay, how lists also gather bad entries, and a safe update process with code.
- Disposable email6 min read
Block disposable emails in Python (Django and FastAPI)
Block disposable email signups in Django and FastAPI with one shared validator, the PyPI blocklist package, offline PSL matching and a fail-open API option.
- Disposable email7 min read
Block disposable emails in Node.js and Express
Express 5 middleware that blocks disposable email signups using a self-refreshing open blocklist or a single API call, with tests and fail-open handling.
- Disposable email7 min read
How to detect disposable email addresses at signup
Four layered checks that catch disposable email at signup: domain normalization, an updating blocklist, MX fingerprinting and DNS signals, with working code.
- Disposable email6 min read
What is a disposable email address, and should you block it?
What disposable email addresses are, how services like Mailinator work, who uses them, and a simple rule for deciding whether your product should block them.