Bad addresses cost more than one lost message. Every hard bounce tells mailbox providers that you send to lists you do not maintain, and enough of them push your next campaign toward the spam folder. Most bad addresses are not exotic: a typo at checkout, a temporary inbox used to grab a discount code, a company that changed domains, or info@ addresses that nobody reads.
This email validator catches those problems before you send. Syntax, typo, disposable, role and free-provider checks run in your browser. The mail server check sends only the domain, the part after the @, to our server, which asks DNS for the domain's MX records. Full addresses never leave your device.
How to validate an email address
- On the Check one email tab, type or paste the address and press Enter or click Validate.
- Keep Check the domain's mail server ticked to include the MX lookup. Untick it for an instant offline check.
- Read the result card. It shows the verdict and one line for each check: syntax, typo, disposable, role address, provider type and mail server, with the MX hosts the domain publishes.
- If a typo is detected, click Use name@suggested-domain to swap in the fix and check again.
Checking a list
- Open the Bulk check tab. Paste one address per line, or paste a whole CSV with a header row. You can also open a CSV or TXT file.
- The email column is found automatically: a header named email, e-mail or Email Address wins; otherwise the column with the most @ signs. All other columns are kept.
- Click Validate list. Up to 500 rows are checked per run. Duplicates are skipped unless you untick that option.
- Filter the table by Valid, Risky, Invalid or Not checked, then download the full results CSV, download only the valid addresses, or copy them.
What each result means
| Result | Meaning | What to do |
|---|---|---|
| Valid | Correct syntax, no warning flags, and the domain publishes mail servers (MX records). | Keep it. |
| Risky | The address could work but has a warning: a likely typo, a disposable domain, a role address, or a domain with no MX record that only has a website address. | Fix typos. Remove disposable addresses. Decide case by case on role addresses. |
| Invalid | Broken syntax, or the domain does not exist, has no mail servers, or publishes a null MX that says it accepts no mail. | Remove it or ask the person again. |
| Not checked | Syntax is fine but the MX lookup was off, failed for the moment, or your daily lookup limit was reached. | Run it again later, or treat it as unconfirmed. |
Valid means "this domain can receive mail and the address is well formed". It does not prove that the mailbox exists. The section on SMTP checks below explains why no free web tool can honestly promise that.
It helps to know the two kinds of bounces. A hard bounce is permanent: the domain does not exist, or the mailbox was closed. Invalid results here predict hard bounces, and you should never send to those addresses again. A soft bounce is temporary: a full inbox, a server that is down, or a message that is too large. Soft bounces usually clear up on their own, and no validator can predict them.
A sample run
Click Load sample list on the bulk tab to run this 9-row CSV, which includes one duplicate:
| Result | Why | |
|---|---|---|
| dana.ortiz@gmail.com | Valid | Google mail servers found; free email provider |
| li.wei@gmail.con | Invalid | .con is not a real extension, so the domain has no mail server; suggested fix li.wei@gmail.com |
| support@shopify.com | Risky | Role address: reaches a shared inbox, not a person |
| deal-hunter@mailinator.com | Risky | Disposable (temporary) email domain |
| mark@@yahoo.com | Invalid | More than one @ sign |
| priya.shah@outlook.com | Valid | Microsoft mail servers found |
| hello@nonexistent-domain-zz91.com | Invalid | No mail server and no address records |
| ana.souza@hotmail.com | Valid | Microsoft mail servers found |
The second Dana Ortiz row is skipped as a duplicate, so 8 rows are checked: 3 valid, 2 risky and 3 invalid. With Apply typo fixes in the download ticked, the results CSV replaces gmail.con with gmail.com and keeps the original in an original_email column, so nothing is lost.
The checks in detail
Syntax
The validator follows the rules of RFC 5321 and RFC 5322 for the kind of address real people use. It rejects a missing or doubled @, spaces, a dot at the start or end of the local part, two dots in a row, characters outside the allowed set, a local part over 64 characters, a domain over 253 characters, an address over 254 characters, domain labels over 63 characters or starting or ending with a hyphen, and IP addresses in place of a domain. Quoted local parts such as "john doe"@example.com are technically allowed by the standard, but almost no signup form or mail provider accepts them, so they are marked invalid. Addresses with non-English letters before the @ are flagged as risky, because they need SMTPUTF8 support that many sending tools still lack.
Typos
The domain is compared with a list of about 100 popular mail providers, such as gmail.com, outlook.com, yahoo.com, icloud.com, hotmail.co.uk, comcast.net and web.de. Known misspellings like gmial.com, gamil.com, hotmial.com and yahooo.com are mapped directly. Others are caught by edit distance: one wrong, missing, extra or swapped letter. Misspelled extensions such as .con, .cmo, .nte and .ogr are fixed for any domain. A suggestion is only shown when the domain is not itself a known provider, so ymail.com is never "corrected" to gmail.com.
Disposable domains
Disposable services hand out inboxes that expire after minutes or days. People use them to grab a coupon or a download without giving a real address. The validator checks against the community blocklist from the disposable-email-domains project on GitHub, which held 9,892 domains in the copy taken on October 15, 2026. The list is released under CC0, a public domain dedication. Subdomains of listed domains match too.
Role and free-provider flags
Role addresses such as info@, sales@, support@, admin@ and noreply@ reach a shared inbox or nobody at all. They are fine for supplier contact but tend to get lower engagement and more complaints in marketing lists, so they are marked risky. Free-provider addresses (about 100 services, including Gmail, Yahoo, Outlook, iCloud and Proton) are only labeled, not penalized; for B2B outreach, a free address often means a very small business or a personal contact.
Mail server (MX) check
For every unique domain, the server asks DNS for its MX records, the list of mail servers that accept email for that domain. If there is no MX record, it checks for an A or AAAA record, because RFC 5321 lets senders fall back to that address. Such domains are marked risky: it can work, but almost every real mail domain publishes MX records. A domain whose only MX record points to "." is a null MX (RFC 7505), which means it accepts no mail at all, and is marked invalid. When the MX hosts reveal the provider, the result names it, for example Google, Microsoft, Zoho or Proton.
Cleaning a list after the check
Download the full results CSV rather than only the valid addresses, so you can decide row by row. A simple routine that works for most stores and agencies:
- Filter the status column to invalid. Delete rows with broken syntax or dead domains. If the row has a typo suggestion and the person is a customer, fix it, or better, ask them to confirm their address at their next order.
- Filter to risky. Remove disposable addresses from marketing lists; they were never meant to receive mail. Keep role addresses for vendors and partners, but think twice before adding info@ addresses to a newsletter.
- Re-run anything marked not checked the next day, when your lookup limit has reset and any temporary DNS failures have cleared.
- Import the rest, and send the first campaign to your most engaged segment before the full list.
Where bad addresses come from
Most typos happen on phones, at checkout and in signup popups, where people type fast and autocomplete fills in a half-remembered domain. Disposable addresses show up when a discount needs an email but nothing else. Dead domains appear in older B2B lists when companies rebrand, merge or close. Knowing the source tells you where to fix it: an email confirmation step at signup stops typos at the door, and a second "is this correct?" prompt on gmial-style domains catches most of the rest.
Why there is no SMTP mailbox check
Some validators connect to the recipient's mail server and start a fake delivery to see whether the mailbox is accepted. We do not, for three reasons. First, it is unreliable: many domains are catch-all and accept every address, others use greylisting and refuse the first attempt from any new sender, and large providers often answer the same way for real and fake mailboxes. Second, mail servers treat repeated probes as abuse, and the probing server's IP address ends up on blocklists. Third, it happens without the address owner's knowledge.
The only proof that a mailbox exists and belongs to the person is a message they act on. For new signups, use double opt-in: send a confirmation link and add the address only after it is clicked.
Limits and privacy
- MX lookups: 30 checks per visitor per day, reset at midnight UTC. One check covers up to 50 domains, and domains checked in the last 24 hours are answered from our cache without counting. A 500-row list with 120 unique domains uses 3 checks.
- Bulk runs check up to 500 rows each. For a longer list, split it and run it in parts.
- Only domains are sent to the server, never full addresses. Lookup results are cached for one day and contain no personal data.
- When the limit is reached, everything except the MX check keeps working.
Tip: Google's sender guidelines ask anyone sending 5,000 or more messages a day to Gmail accounts to authenticate with SPF, DKIM and DMARC, offer one-click unsubscribe, and keep the spam complaint rate in Postmaster Tools below 0.3%, with 0.1% as the target. A clean list is the easiest part of meeting those rules. The full requirements are in Google's email sender guidelines.
Where this fits in your workflow
Run the validator on any list before you import it into Klaviyo, Mailchimp, Shopify Email or your CRM, and again on old segments before a re-engagement campaign. If the addresses are buried in documents or exports, the email extractor pulls them out first, and the results CSV opens straight in the CSV to Excel converter if your team prefers a spreadsheet.
For agencies and freelancers who prospect local businesses, Local Lead Finder Pro in AM Jarvis collects business contacts from Google Maps listings and their websites, scores weak profiles and writes the outreach, so the list you validate starts out targeted. Our guide to finding local SEO leads shows the full process.