Email Validator Tool

What this email validator checks

Most free tools stop at the first layer: they read the domain's DNS and call it a day. This email validator runs all three layers and shows you the raw records behind every verdict, so you can see exactly why an address passed or failed instead of trusting a green tick.

How to validate an email address, step by step

The whole process takes about five seconds. What matters is reading the result properly, because a status on its own does not tell you what to do next.

Understanding your result

Every check returns one of five statuses. They are ordered by how confident the answer is, not by how good the address looks.

Why "risky" is not the same as "bad"

Risky covers two very different situations. A disposable address is a deliberate throwaway and is usually worth blocking — you can check whether a domain is disposable on its own if you are screening signups in bulk. A catch-all domain, on the other hand, is often a perfectly normal company that routes everything through a filtering service — the address may be entirely real, it simply cannot be proven from outside. Read the Layer 3 panel to see which of the two you are looking at before deciding.

How to read the DNS records

Layer 1 prints the domain's actual records. Here is what each one is telling you.

MX records and priority

An MX record names the server that accepts mail for a domain. A domain can list several. The priority number decides the order sending servers try them, and lower wins — priority 1 is attempted before priority 10, which is the backup. Multiple MX records is a sign of a properly run domain, not a problem.

If the MX list is empty, nothing else matters: the domain cannot receive mail, and every message you send will hard-bounce. A live website is no guarantee here — plenty of domains host a site and never configure mail at all.

The hostname usually reveals who actually runs the mailbox:

SPF — who is allowed to send as this domain

An SPF record is a single line listing the servers permitted to send mail using that domain. The part that matters is at the end. -all means anything from anywhere else is rejected outright. ~all is a soft fail — other servers are allowed through but flagged. ?all states no opinion, and +all lets literally anyone send as the domain, which is a serious misconfiguration. A domain with no SPF record at all is far easier to spoof, and its own mail is more likely to land in spam.

DMARC — what happens when a check fails

DMARC ties SPF and DKIM together and tells receiving servers what to do with mail that fails. p=none is monitoring only: failing mail is still delivered. p=quarantine sends it to spam. p=reject throws it away. A domain on p=reject is actively defending its name, which is a good signal when you are judging whether an address belongs to a real, maintained organisation.

What the mailbox check does — and where it stops

The mailbox check is the layer most free tools skip, and it is the only one that can tell you whether an inbox genuinely exists.

It works by opening a connection to the domain's highest-priority mail server and starting an ordinary SMTP conversation — the same one every mail server on the internet has thousands of times a day. It gets as far as naming the recipient and then stops. The server's reply is the answer: an acceptance means the mailbox exists, a permanent rejection means it does not. No message is ever composed or delivered, because the conversation ends before the stage where a message body would be transmitted.

Immediately afterwards it names a second, randomly generated address at the same domain. If the server accepts that one too, the domain accepts everything — a catch-all — and the first answer proved nothing.

Where the check cannot help you

• Google Workspace and Microsoft 365 domains. Both deliberately accept every recipient at this stage to stop attackers harvesting valid addresses. Mailboxes hosted there cannot be individually confirmed by us or by any other service. You will see risky or unknown, never a false deliverable.
• Catch-all domains. A real mailbox and a typo get an identical answer. The verdict is risky by design.
• Greylisting. Some servers defer a first-time connection on purpose. That returns unknown, and a retry a few minutes later usually resolves it.
• Full or suspended inboxes. A mailbox can exist, pass every check, and still bounce your message tomorrow because it is over quota or the employee has left.
• Free providers. Gmail, Outlook, Yahoo and similar hosts are trusted rather than probed, which avoids tripping their rate limits.

How the confidence score works

The confidence score runs from 0 to 100% and reflects how much of the evidence actually confirmed the address, rather than merely failing to contradict it. Since the mailbox check went live, the score is driven mostly by what the mail server said.

A workable rule: accept at 70% and above, review between 40% and 70%, reject below 40%. If you are cleaning a cold outreach list, raise the accept line to 80% — the cost of one hard bounce to your sender reputation is higher than the cost of dropping one uncertain contact.

Email validator vs email checker vs email verifier

The three terms get used interchangeably, but they describe different depths of checking, and knowing the difference tells you what a given tool is actually doing.

An email checker is normally the shallowest: syntax and perhaps whether the domain exists. It answers "could this be an address?" and nothing more. An email validator adds the infrastructure and reputation layers — MX, SPF, DMARC, disposable and role-based flags — which answers "can this domain receive mail, and should I trust it?" An email verifier goes one step further and asks the mail server itself whether the individual mailbox exists.

This tool does all three. It validates the address, checks the domain's reputation, and verifies the mailbox where the receiving provider allows it — which is why the result is a report rather than a single word.

Who uses this tool

The same check solves quite different problems depending on where in a business it sits.

How Sigma Wire compares to other free email tools

Free email checkers differ mostly in what they hide. This table covers the things that change what you can actually do with the result. Figures reflect each provider's published free tier as of July 2026.

Competitor tiers change without notice. If you spot a row that is out of date, tell us and we will correct it.

Our methodology and limitations

Sigma Wire is a Corenexis product, and this tool runs on the Corenexis Email Validator API — the same engine that powers the paid API, with no reduced accuracy on the free web version.

What we check, in order

Syntax is evaluated first, because an invalid address makes every later check pointless. Then DNS: whether the domain resolves, and what its MX, SPF and DMARC records contain, read live at the moment you press the button rather than from a stored copy. Then reputation: the domain is matched against a disposable list of more than 405,000 entries, refreshed continuously, and the local part is matched against known role-based prefixes. Finally the mail server itself is contacted for the mailbox and catch-all checks.

What we do with the address you enter

Addresses are used to perform the check and are not stored against your session or sold. Results are held in a short-lived cache for a few minutes so that repeated or shared checks return instantly, and are then discarded. No message is ever sent to any address checked here.

What this tool cannot tell you

• Whether a mailbox on Google Workspace or Microsoft 365 exists — those providers do not expose it to anyone.
• Whether a confirmed mailbox is actively monitored, or abandoned years ago.
• Whether an address belongs to the person who gave it to you.
• Whether a message will land in the inbox rather than the spam folder — that depends on your sending reputation, not on the recipient.

Related tools

Frequently asked questions