Email verification checks whether an address can receive mail before you send to it. Sending to invalid addresses causes hard bounces, and high bounce rates make mailbox providers trust all your mail less.
What a verification checks
- Syntax — is it a valid address format?
- Domain — does the domain exist?
- MX records — does the domain accept email?
- Mailbox — does the server accept this specific mailbox? This is asked over SMTP without sending a message
- Risk flags — disposable addresses, role addresses (info@, sales@), catch-all domains
Understanding the results
- Valid — the server accepted the mailbox
- Invalid — the mailbox or domain does not exist; remove it
- Catch-all / accept-all — the domain accepts every address, so a single mailbox cannot be confirmed
- Unknown — the server did not answer clearly (timeouts, greylisting); try again later
When to verify
- At sign-up, to stop typos and fake addresses
- Before a campaign to a list that has not been mailed for a few months
- After importing contacts from events, CRMs or old systems
Inbox CheckerCheck a single address now, or upload a CSV for bulk verification in your account.
Open Inbox Checker →Never buy email lists. Verification removes invalid addresses, but it cannot make people who never opted in want your mail.
Frequently asked questions
Does verification send an email to the address?
No. It talks to the receiving server and stops before any message is transmitted.
Why are some results unknown?
Some servers hide mailbox status, use greylisting or rate-limit checks. Unknown is not the same as valid.
How often should I clean my list?
Every few months for active lists, and always before mailing a list that has been dormant.