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Mailcleaner guide · Updated 5 November 2026
What is email verification, and how does it work?
Email verification checks whether an email address can receive mail before you send to it. A verifier tests the address format, finds the domain's mail servers, asks the server whether the mailbox exists without sending a message, and flags risky types such as disposable, role and catch-all addresses.
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01 / 05
What is email verification?
Email verification (also called email validation) is the process of checking that an address is real and able to receive email. It answers one practical question: if I send to this address, will it be delivered, or will it bounce?
Bounces matter because mailbox providers such as Gmail, Yahoo and Outlook watch how many of your messages bounce. A high bounce rate tells them you send to lists you don't look after, and more of your mail starts landing in spam, including mail to good addresses.
02 / 05
What checks does an email verifier run?
A good verifier runs several checks in order, cheapest first, and stops when one gives a definite answer. Flaxxa Mailcleaner runs these:
- Syntax: is the address correctly formed?
- Typos: is the domain a near-miss of a big provider, such as gmial.com for gmail.com?
- Disposable: is the domain a known throwaway inbox service?
- Role: is it a shared address such as info@, sales@ or support@?
- MX lookup: does the domain have mail servers at all?
- SMTP check: does the mail server accept this mailbox? The verifier starts a delivery and stops before any message is sent.
- Catch-all: does the server accept every address, so a yes means nothing?
- Extra signals on deeper checks: spam-trap patterns and a domain blocklist lookup.
03 / 05
What do email verification results mean?
Most verifiers sort addresses into a few groups. Flaxxa Mailcleaner uses eight verdicts, each with a reason code and a 0–100 risk score:
- Valid: the mailbox exists. Safe to send.
- Invalid: it will bounce (no mailbox, no mail server, or bad syntax). Remove it.
- Catch-all: the domain accepts everything, so the mailbox can't be confirmed. Send with care.
- Risky: the check couldn't settle it, or it matched a risk pattern.
- Disposable: a temporary inbox. Usually remove.
- Role-based: a shared inbox like info@. Fine for some mail, poor for marketing.
- Unknown: the server didn't answer in time. Try again later.
- Abuse: a past complainer. Don't mail.
04 / 05
What can't email verification tell you?
Verification is strong evidence, not a promise. Some providers, Yahoo among them, accept every address at the SMTP step or refuse checks from verification servers, so the mailbox can't be confirmed that way. Catch-all company domains behave the same. A good verifier says so plainly instead of calling those addresses valid.
Verification also can't tell you whether someone wants your email. A valid address that never opens still hurts engagement, so pair verification with sending only to people who asked to hear from you.
05 / 05
When should you verify email addresses?
Before a big send
Clean any list that is old, imported or bought-in before you mail it.
On a schedule
Re-check lists every few months, because a few percent of addresses go stale each year.
After bounces
Suppress every hard bounce so you never mail that address again.
FAQ
How email verification works: common questions
In practice, yes. Some people use validation for the format check and verification for the full mailbox check, but most tools use the words for the same thing.
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Mailcleaner features for this
The checks
The checks behind each verdict: syntax, typo, disposable and role detection, MX lookup, an SMTP mailbox check, catch-all detection and deeper signals.
Email verification
Verify one email address or a whole list: a verdict, a 0–100 risk score and a confidence score for each, from a paste, a file, Google Drive or the API.
Catch-all detection
Find catch-all (accept-all) domains in your email list. Flaxxa Mailcleaner tests each server, scores catch-all domains and never passes them off as valid.
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