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Notes from the edge
B2B signup quality, email intelligence, Workspace and Microsoft 365 detection — and what we learn running a free API.
Check business emails from your AI assistant with MCP
Connect isBusinessEmail's MCP server to Claude, ChatGPT, Cursor or VS Code, then ask which emails are work emails and which companies use Microsoft 365.
Read the postDomain age as a fraud signal: what a new domain tells you at sign-up
A domain registered days ago is a real risk signal at sign-up, not proof of fraud. How to check domain age with RDAP and when to review instead of block.
Are .edu, .ac.uk and .gov emails business emails? Education and government addresses explained
School, university and government addresses like .edu, .ac.uk and .gov are organizational, not personal. How they are classified and when it matters.
Email relay addresses: privaterelay.appleid.com, mozmail.com and duck.com explained
Relay addresses on privaterelay.appleid.com, mozmail.com or duck.com forward to a hidden real inbox. How they work and how B2B sign-ups should handle them.
Email typo domains: catch gmial.com and suggest the fix
Email typo detection compares the domain with popular providers and offers a fix, like gmial.com to gmail.com. How it works, what typos cost, how to show it.
Free trial abuse: the email signals that catch it, and where they stop
Stop repeat free-trial sign-ups with email signals: disposable and relay inboxes, +tag and Gmail-dot variants, typo domains, new domains and a blocklist.
Lookalike and punycode email domains: spotting homographs at sign-up
Lookalike domains imitate gmail.com or paypal.com with Cyrillic letters, digits or rn for m. How punycode exposes them and how isBusinessEmail flags them.
Plus addressing and Gmail dots: how to deduplicate sign-ups
Plus addressing sends jane+news@acme.io to jane@acme.io, and Gmail ignores dots. How to deduplicate sign-ups with a key, without blocking anyone.
Role-based email addresses: should you accept info@ at sign-up?
Role-based email addresses like info@ and sales@ belong to a team, not a person. When to allow, review or block them at sign-up, in marketing and in sales.
Shared inbox vs group email: how to tell from the address
A shared inbox is one mailbox a team answers from; a group forwards to many members. Why DNS can't tell them apart, and what the address name can.
Business email vs personal email: what's different and why it matters
Business email vs personal email: how they differ in ownership, security, offboarding, deliverability, cost and integrations, and when each is fine.
Check for a business email in JavaScript, Python and PHP
Check for a business email in JavaScript, Python and PHP: a free-provider list plus MX lookup you can run today, its pitfalls, and calling an API safely.
Email verification vs email classification
Email verification vs email classification: one checks whether an address can receive mail, the other what kind of address it is. When you need both.
How to find someone's business email address
How to find someone's business email address: company pages, email patterns, search operators and finder tools, then how to check it before you send.
Free email providers: the list and what counts as personal
A list of free email providers worldwide, from Gmail and Outlook to GMX, Yandex, QQ and Naver, plus ISP and privacy mailboxes, and what counts as personal.
How to tell if an email is a business email
How to tell if an email is a business email: read the domain, compare it with free provider lists, look up MX records and rule out disposable addresses.
Lead scoring by email domain
Lead scoring by email domain: why the domain is a strong signal, an example scoring model, routing to sales, CRM enrichment, pitfalls and measuring it.
How to require a work email at sign-up (without losing good users)
How to require a work email at sign-up: choose block, review or allow per category, write error messages that work, fix typos, plan exceptions, fail open.
What is a business email? Definition, examples and edge cases
A business email is an address on an organization's own domain, like jane@acme.io, not a shared one like gmail.com. Definition, examples and edge cases.
How to find out which email provider a company uses
How to find out which email provider a company uses: read its MX records, see past security gateways, then check SPF, DKIM and Microsoft 365 tenant data.
Why we built isBusinessEmail
Personal-email signups kept stalling our B2B onboarding at the integration step. Here's the internal check we built, and why we made it a free API.
Google Workspace vs Gmail: tell them apart from DNS
How to tell a Google Workspace domain from consumer Gmail using MX, DKIM and SPF records, where DNS misleads you, and the hd claim at sign-in.
Microsoft 365 tenant vs Outlook.com: what your integration can and can't do
Microsoft 365 work accounts vs Outlook.com accounts: admin consent, SharePoint, OneDrive for Business, Teams, and finding a tenant before sign-in.
Should B2B SaaS block free email signups?
The trade-offs of blocking Gmail and Outlook signups on a B2B product, the middle paths that keep good users, and how to decide with your own data.
The disposable email problem (and why lists aren't enough)
Why disposable email lists always lag behind, how throwaway services evade them, and the DNS and domain signals that catch what lists miss.
Detecting business emails with MX records
What MX records reveal about an email domain (Workspace, Microsoft 365, gateways, hosting, forwarding), what they can't tell you, and pitfalls in code.