free email verifier
Verify any email address free with the checker solving B2B emails
Validate any email address in seconds. No signup needed. Most free verifier tools stop at syntax and MX records. Allegrow solves verification on B2B contacts at catch-all domains and secure email gateways, where other tools give up and return “Unknown”
How the email verification works?
Syntax and format
The first check confirms the address structurally. Allegrow validates against RFC 5322. This is the standard defining a legal email address ensuring for fundamental errors invalids are returned fast.
Domain & MX lookup
Allegrow queries DNS for the domain's MX records. The entries telling the internet which servers handle its mail and returns the provider behind them (Google/ Microsoft etc).
SMTP mailbox check
Allegrow opens an SMTP connection, to verify inbox existence. This at scale resolves rate limit, greylisting, quality IP assigment, and result interpretation.
Definitive Catch-All Verification
Legacy tools shrink your TAM by marking catch-alls as "Unknown". We provide “Valid/Invalid” statuses where others fail, unlocking 30% more net-new valid contacts with precision, eliminating false negatives.
Advanced Risk Detection
Go beyond basic statuses to distinguish legitimate users from non-primary aliases, spam traps, disposables, and dead inboxes so you don't reduce accuracy by counting abandoned inboxes as valid.
Primary B2B Email Detection
Legacy tools return multiple valid addresses for one executive. We identify the primary mailbox with the primary tag, so you can reach the decision-makers active inbox, not an unmonitored account.
Other ways Allegrow lets you verify emails
Email Verifier Accuracy Guide
See how Allegrow provided 98.22% accuracy across a test of 10,000 email addresses for free, and how to create your own accuracy test from scratch. Results on over 100,000 tests across the most popular checkers in the market wuth accuracy results.
Access full guide
Frequently asked questions
Is this email verifier really free?
Yes. Single-address verification is free with no account, no API keyand no credit card. There are some caps on overall usage and protection by Cloudflarefrom bots, this is the only restriction. If you need to verify a large list, afree trial of our bulk verifier covers 1,000 addresses.
What is the best free email verifier?
It depends on what type of emails you are verifying. Many free tools like NeverBounce are accurate on consumers like gmail.com and return “Unknown” on many corporate domains. If you verify business addresses our benchmark study found Allegrow had the best coverage at 98.2% on enterpise domains. Whereas, options like Hunter were strong on small business domains.
Can I verify a list of emails for free in bulk?
Yes. Our free trial includes 1,000 verifications by CSV upload. Beyond this to integrate your CRM like Hubspot or Sales Engagement Platform like Outreach or Salesloft you can move onto on of our other plans.
Do I need an API key to use this email verifier?
No. The tool on this page runs in your browser with no API key, no token and no authentication of any kind. An API key is only needed if you want to verify addresses programmatically from your own application, a form, or a data pipeline. If you do need an API key this can done in-app while using our API docs for guidance on endpoint selection.
Why you need an email verifier?
Because sending to an address that doesn't exist means your overall usage of the email channel is less successful. Mailbox providers treat bounces as evidence you don't know your audience, and that lowers the sender reputation deciding whether your next campaign reaches the inbox. Verification removes bounces, spam traps and dead mailboxes before they enter a sequence, flags contacts who have changed jobs, and identifies which of a person's addresses is their primary inbox.