Email verifiability checker: how much of your list can actually be verified?
In short: Paste a list and see, domain by domain, whether a mailbox check can give a definite answer, will come back risky, or is on a domain with no MX record, before you check anything. Limit: It predicts what a mailbox check can confirm on each domain; it doesn't check any mailbox, so it can't tell you which addresses are real.
An email verifiability checker tells you, before you verify, how much of a list can get a definite answer. Paste addresses and each domain is sorted: providers that answer per mailbox (Gmail, Proton), company domains, providers that always come back risky (Yahoo, Outlook.com, iCloud) and domains with no MX record. Only domains are sent; no mailbox is checked.
By SimpleVerifier Team · Last updated
How do I check which emails on a list can be verified?
- Paste email addresses, one per line, or upload a CSV. The addresses are read in your browser and grouped by domain.
- Press Check what can be verified. Only the unique domains are sent: consumer providers are matched against our published provider tests, and every other domain gets one MX and SPF lookup.
- Read the split: usually a definite answer, depends on the company, expect risky, and likely to bounce, counted by addresses, not domains.
- Download the CSV, or send the addresses that can get an answer straight to a mailbox check.
Example
- You enter
- Ten addresses: two at
gmail.com, one each atyahoo.com,outlook.com,icloud.com,hotmail.comandproton.me, two at company domains on Google Workspace, and one at a domain with no MX record. - You get
- About 5 of 10 can get a per-mailbox answer: Gmail and Proton (3) answer per mailbox and the two company domains are answered unless catch-all. Yahoo, Outlook.com, Hotmail and iCloud (4) are marked expect risky, and the domain with no MX (1) likely to bounce. The 5 answerable addresses can go straight to a mailbox check.
- Limits
- Up to 100 unique domains a run without an account and 500 when signed in with Google. Only domains are sent; one MX and SPF lookup per company domain, no SMTP.
Why does an email verifier return risky or unknown for some addresses?
Because some mail servers won't say whether a single mailbox exists. A verifier asks the recipient's server at the RCPT TO step of an SMTP conversation and hangs up before sending; that only works when the server answers honestly. Yahoo and AOL accept any recipient, real or made up, so every address there looks the same. Microsoft's consumer mail (Outlook.com, Hotmail, Live, MSN) and Apple's iCloud don't give a dependable answer about single mailboxes, so our checker never probes them and returns those addresses as risky by design.
Company domains are different: the checker offers a made-up address first. If the server accepts it, the domain is catch-all and no single address can be confirmed; if it rejects it, each real address gets its own valid or invalid answer. That is why this tool marks company domains "depends on the company" rather than guessing. The provider-by-provider results are in our study of how mailbox providers answer verification checks.
How do I know how much of my email list can be verified?
Paste the list above. Each address is counted under its domain, and each domain gets one of four outlooks. Gmail, Proton, Yandex and Zoho addresses usually get a definite answer. Company domains get a per-mailbox answer unless they turn out to be catch-all. Yahoo, AOL, Outlook.com, Hotmail and iCloud addresses come back risky with any verifier. Domains with no MX record, or a null MX, are marked likely to bounce: RFC 5321 lets mail fall back to the domain's own address, but few real mail domains work that way.
The split is counted by addresses, so a list that is half Gmail and half Yahoo shows about half as "definite" and half as "risky". If a large share is risky, plan how you'll treat risky results before you verify, rather than being surprised after.
What should I do with addresses that can't be verified?
Treat them as a separate segment. Risky consumer addresses that came from a real signup with double opt-in, or that opened recent mail, are usually safe to keep. Risky addresses on a bought or scraped list are the ones to send to slowly, in small batches, watching bounces, or to drop. Addresses on domains with no MX record are the first to remove.
For company domains, verify first: most get a per-mailbox answer, and the catch-all ones are then known. Our guide to accept-all versus unknown results covers what each status means and how to send to it.
What does this tell you that a provider lookup doesn't?
| This tool | Email provider lookup | |
|---|---|---|
| Names the mail provider | Yes, for company domains | Yes |
| Says whether a mailbox check can confirm addresses there | Yes, per domain | No |
| Counts the share of your list in each outcome | Yes, by address | Counts by provider |
| Checks whether a mailbox exists | No | No |
Who uses this tool, and for what?
- Newsletter creators
- See how much of a consumer-heavy list is Yahoo, Outlook.com or iCloud before you verify, so a large risky share doesn't come as a surprise.
- Cold emailers
- Check a lead list's company domains get a per-mailbox answer, and drop the domains with no MX record before you spend a mailbox check on them.
- Agencies
- Show a client, before the cleaning run, what share of their list can be confirmed and what will stay risky with any verifier.
- Ecommerce
- Split a customer export into addresses that can be confirmed and ones to judge by recent opens and orders instead.
What can’t this tool tell you?
- It predicts what a mailbox check can confirm on each domain; it doesn't check any mailbox, so it can't tell you which addresses are real.
- Whether a company domain is catch-all is only known once it is probed, so company domains are marked "depends on the company".
- Provider behaviour is from our published tests and can change; a provider that answers today can start refusing checks later.
- Consumer providers we haven't tested are shown as not known yet rather than guessed.
- Up to 100 unique domains a run without an account, 500 after a free Google sign-in.
Common questions
- Can you verify Yahoo email addresses?
- Not one by one. Yahoo's servers accept any recipient during the SMTP conversation, including made-up ones, so a verifier can't tell a real mailbox from a fake. Our checker returns Yahoo and AOL addresses as risky with the reason "Accepts all addresses" rather than calling them valid.
- Why are Outlook.com, Hotmail and iCloud addresses always risky?
- Microsoft's and Apple's consumer mail doesn't give a dependable answer about single mailboxes, so our checker never sends them a mailbox probe. Those addresses come back risky with the reason "Provider hides mailbox status". Company domains on Microsoft 365 are different and are probed like any other company domain.
- Does this tool check whether the emails exist?
- No. It checks no mailbox and sends no email. It tells you what a mailbox check is able to confirm on each domain, from our published provider tests and the domain's MX record. To find out which addresses exist, run a mailbox check.
- Which email providers can be verified?
- Gmail, Proton, Yandex and Zoho answer mailbox checks one address at a time in our tests. Most company domains do too, unless they are set up as catch-all. Yahoo, AOL and Mail.ru accept every address, and Outlook.com, Hotmail, Live, MSN and iCloud are not probed, so those come back risky.
- Are my email addresses uploaded?
- No. The list is read in your browser and only the unique domains are sent to our server. Consumer providers are answered from our published provider data; other domains get one MX and SPF lookup in public DNS.
- Is this email verifiability checker free?
- Yes, it's a free tool with no card or payment. Up to 100 unique domains a run without an account, or 500 after a free Google sign-in.
Sources
A tidy list can still be full of dead addresses.
Extracting, deduplicating and syntax checks all work on the text of an address. None of them can tell whether the mailbox exists. Only the server that hosts it can answer that, through an SMTP check, and that is what the paid product does.
- Upload the cleaned file as it is: CSVs up to 100,000 rows
- A real SMTP mailbox check on every row, with catch-all detection
- Small list? Starter at $9/mo covers 2,500 emails a month, cancel anytime
One plan, cancel anytime, no contract. Sign in with Google and your first 100 email checks are free, no card. The free tools stay free either way.