Free tool Email checker and email validator: clean a list before you send to it
Paste the addresses you collected from a form, a chat widget or a spreadsheet. Each one is checked against the email syntax rules, common typos such as gmial.com, a public list of disposable-mail domains and your other rows. When you are ready, look up whether each domain can receive mail at all.
- Up to 20,000 addresses
- No SMTP probing
- List stays in your browser
Check and clean addresses
One address per line, or a column pasted from a spreadsheet. "Name
" and CSV rows work too. The sample mixes the usual problems; try the CRM export and edge-case samples as well.Separated by new lines, commas, semicolons or tabs. Up to 20,000.
Used only when you click "Check MX". Only the domain part (after @) of each address is sent.
Addresses
14
Valid
7
Unique, no problems found.
Review
3
Valid syntax, but a typo, disposable domain or similar.
Invalid
3
Cannot be delivered as written.
Duplicates
1
Removed from the clean list.
Summary
- Invalid3 invalid: they cannot be delivered as written. Fix the obvious ones (a missing letter, a space) or drop them.
- Review2 look like typos of a common mailbox domain. Mail to them usually bounces or reaches a stranger; confirm before fixing.
- Review2 use a disposable-mail domain. The inbox may stop existing within minutes or days.
- Note1 duplicates removed from the clean list.
- Note1 are role addresses such as info@ or support@. Fine for B2B replies; keep them out of marketing lists if your provider asks you to.
- Note1 use +tags. They reach the same inbox; keep the tag, it tells you where the address came from.
- Note1 use an international domain name, shown with its ASCII (xn--) form.
- NoteMX records not checked yet. "Check MX records" looks up the 9 unique domains with the DNS-over-HTTPS service selected above.
Every address
Problem rows first. Click "Check MX" to fill the last column.
| Line | As pasted | Cleaned | Status | First problem | MX |
|---|---|---|---|---|---|
| 8 | marta..lopez@example.org | marta..lopez@example.org | Invalid | Two dots in a row before @ | — |
| 9 | owen@example | owen@example | Invalid | No top-level domain (like .com) | — |
| 14 | nobody-at-example.com | nobody-at-example.com | Invalid | No @ sign | — |
| 4 | jonas.weber@gmial.com | jonas.weber@gmial.com | Review | Possible typo: did you mean jonas.weber@gmail.com? | Not checked |
| 5 | camila@outlook.con | camila@outlook.con | Review | Possible typo: did you mean camila@outlook.com? | Not checked |
| 7 | test1234@mailinator.com | test1234@mailinator.com | Review | Disposable / temporary mail domain | Not checked |
| 2 | maya.chen@example.com | maya.chen@example.com | Duplicate of line 1 | — | Not checked |
| 1 | maya.chen@example.com | maya.chen@example.com | Valid | — | Not checked |
| 3 | Jonas.Weber@Example.org | jonas.weber@example.org | Valid | — | Not checked |
| 6 | support@shop.example.net | support@shop.example.net | Valid | Role address (team inbox, not a person) | Not checked |
| 10 | first.last+chat@gmail.com | first.last+chat@gmail.com | Valid | Has a +tag | Not checked |
| 11 | firstlast@gmail.com | firstlast@gmail.com | Valid | — | Not checked |
| 12 | hana@exämple.de | hana@exämple.de | Valid | International domain, sent as xn--exmple-cua.de | Not checked |
| 13 | kim@yahoo.com | kim@yahoo.com | Valid | — | Not checked |
maya.chen@example.com
jonas.weber@example.org
support@shop.example.net
first.last+chat@gmail.com
firstlast@gmail.com
hana@exämple.de
kim@yahoo.comValid, unique, lowercase where chosen. Ready to import.
jonas.weber@gmial.com → jonas.weber@gmail.com
camila@outlook.con → camila@outlook.com
test1234@mailinator.comValid syntax but risky. Typos show the likely fix.
email,status,problems,mx
maya.chen@example.com,valid,,
maya.chen@example.com,duplicate,,
jonas.weber@example.org,valid,,
jonas.weber@gmial.com,risky,typo disposable,
camila@outlook.con,risky,typo,
support@shop.example.net,valid,role,
test1234@mailinator.com,risky,disposable,
marta..lopez@example.org,invalid,dotDot,
owen@example,invalid,noTld,
first.last+chat@gmail.com,valid,subaddress,
firstlast@gmail.com,valid,,
hana@exämple.de,valid,idn,
kim@yahoo.com,valid,,
nobody-at-example.com,invalid,noAt,Status and problem codes per address, for a spreadsheet.
Version v1.0Updated Update history
Valid, review, invalid, duplicate
Every address lands in one bucket; the summary says why.
Valid
The syntax follows the email standards, the domain has a real top-level domain, and nothing else looks wrong. After an MX check, valid also means the domain publishes where its mail goes. It does not mean the mailbox exists: only sending (or the recipient replying) proves that.
Review
Deliverable as written but risky: a likely typo (gmial.com), a disposable domain, a quoted or non-ASCII name, or a domain with no MX record. Typos list the probable fix; ask the person rather than silently correcting.
Invalid
Cannot be delivered as written: no @, two dots in a row, spaces, a missing top-level domain, a domain that does not exist or one that publishes a Null MX to say it takes no mail.
Duplicate
The same address after lowercasing (and, if you tick the option, Gmail dot and +tag variants). The first occurrence is kept, later ones point back to its line.
An address can be valid and still bounce: the mailbox may have been closed or be full. Tools that "verify" mailboxes do it by starting an SMTP conversation with the receiving server; this one deliberately does not, because many servers block or blacklist that and some always say yes.
Three steps
Nothing to install. Results update as you type.
-
1
Paste the list
Copy the email column from your CRM, spreadsheet or form export. Names in angle brackets and extra CSV columns are fine.
-
2
Check MX (optional)
Click "Check MX records" to see which domains do not exist or do not take mail. Pick a DNS service you trust; in mainland China, Alibaba Cloud DNS is usually reachable when the others are not.
-
3
Copy or download
Copy the clean list for import, fix the review rows by hand, and download the CSV if you need the status of every row.
What counts as a valid address
The rules come from the SMTP and message-format standards. This tool checks the practical subset that real mail systems accept, and says so when an address is technically valid but unlikely to work.
- Before @: letters, digits and
! # $ % & ' * + / = ? ^ _ ` { | } ~ -, with dots allowed but not first, last or doubled (RFC 5322 §3.2.3); up to 64 bytes (RFC 5321 §4.5.3.1.1) - After @: domain labels of letters, digits and hyphens, 1–63 characters each, not starting or ending with a hyphen; 253 characters in total; international domains are converted to
xn--form first - Whole address: up to 254 characters (RFC 5321 path limit minus the angle brackets)
- Not supported: comments such as
john(work)@example.comand the obsolete syntax; quoted names and IP-literal domains are accepted but flagged - MX: a domain with no MX record falls back to its A / AAAA address (RFC 5321 §5.1);
MX 0 .is a Null MX meaning "no mail accepted" (RFC 7505)
| Check | Catches | Cannot catch |
|---|---|---|
| Syntax | Missing @, spaces, double dots, bad characters | A well-formed address nobody owns |
| Typo list | gmial.com, hotmial.com, outlook.con | Typos in the name before @ |
| Disposable list | 8,883 domains from a public, community list | New or private throwaway domains |
| MX lookup | Non-existent domains, domains that take no mail | Whether this mailbox exists |
Cleaning the sample list
What the validator does with the 14 lines in the default sample.
| Input | Bucket | Why |
|---|---|---|
Maya Chen <maya.chen@example.com> and maya.chen@example.com | Valid + duplicate | The name is dropped; the second line is the same address |
jonas.weber@gmial.com, camila@outlook.con | Review | Typos of gmail.com and outlook.com |
test1234@mailinator.com | Review | On the public disposable-domain list |
marta..lopez@example.org, nobody-at-example.com | Invalid | Two dots in a row; no @ at all |
owen@example | Invalid | No top-level domain: the address stops before .com, .org or similar |
first.last+chat@gmail.com and firstlast@gmail.com | Valid, both | Tick "Merge Gmail variants" and the second becomes a duplicate |
support@shop.example.net, hana@exämple.de | Valid, with a note | A role address; an international domain sent as xn--exmple-cua.de |
Click "Check MX records" and the example.com, example.org and example.net addresses move to Invalid: those domains are reserved for documentation (RFC 2606) and publish a Null MX. Real domains such as gmail.com and yahoo.com show their mail servers.
How lists go bad
A few habits cause most bounces.
Auto-correcting typos
gmial.com is almost always gmail.com, but not always. Change it after the person confirms, or you may email a stranger.
SMTP "verification" services
Probing mailboxes over SMTP gets your IP throttled or listed, and many servers answer "yes" to everything. A bounce after a real send is the reliable signal.
De-duplicating case-sensitively
Maya@Example.com and maya@example.com are one person. Lowercase before comparing, or the same customer gets every email twice.
Deleting role addresses blindly
info@ or support@ is often the only contact a small business has. Keep them for replies; just leave them out of bulk marketing if your sending provider asks you to.
Where these addresses come from
Outside working hours, the TapCub chat widget collects a message and an email address. Those offline messages land in the same inbox as live chats.
Offline messages
Visitors leave an email and a question when nobody is online; you reply by email. Check the address before you do.
Learn moreWorking hours per site
Set the hours, and outside them the widget switches to the offline form automatically.
Learn moreHosted chat page
A chat link for email signatures and social bios that lands in the same inbox.
Learn moreEmail validator questions
Still have a question?
Chat with the team behind TapCub — we usually reply within a few hours on business days.
How do I check if an email address is valid?
Paste it above. The validator checks the syntax against the email standards, flags typos of common domains and disposable-mail domains, and, when you click "Check MX records", whether the domain can receive mail. Whether the mailbox itself exists can only be confirmed by sending to it.
Can it tell whether a mailbox exists?
No, on purpose. The only way to ask is to open an SMTP connection to the recipient's server and pretend to send. Many servers block that, rate-limit it, or accept every address, and repeated probing can get your IP listed. A real send and its bounce report are the reliable test.
What is an MX record?
The DNS record that names the servers accepting mail for a domain. No MX record means mail falls back to the domain's web address, which usually does not accept mail; a Null MX (0 .) says the domain takes no email at all; a domain that does not exist cannot receive anything.
Is my list uploaded anywhere?
No. Everything except the MX lookup runs in your browser. The MX lookup sends only the domain names (for example gmail.com, not the full address) to the DNS-over-HTTPS service you pick: Cloudflare, Google or Alibaba Cloud.
Where does the disposable-domain list come from?
From the community-maintained disposable-email-domains project on GitHub (public domain, CC0), 8,883 domains in the copy used here. It misses new or private throwaway domains and occasionally lists a domain that someone uses for real mail, so those addresses go to Review rather than Invalid.
Are uppercase letters in an email address a problem?
No. Domains are case-insensitive, and although the standard allows the part before @ to be case-sensitive, all major mailbox providers ignore case. Lowercasing makes duplicates easy to spot.
Why is user+tag@gmail.com not treated as a duplicate?
Because it is a different address, and the tag tells you where the person signed up. Gmail delivers it to the same inbox; tick "Merge Gmail variants" if you want one row per Gmail inbox. Other providers handle dots and tags differently, so the option only applies to @gmail.com.
Update history
New features, fixes and data refreshes for this tool, newest first.
-
· v1.0
LaunchedFirst release.
Data this tool relies on
- Disposable email domains and IANA top-level domains — checked 2026-11-10, reviewed every 3 months (next review by 2027-02-10)
Missing something or found an error? Tell us — requests that come up often go into the next update. All tool updates
Answer visitors while they are still on the page
Fewer offline messages means fewer addresses to clean. TapCub live chat shows each visitor's page and source, and AI can answer from your knowledge base first.