Bulk email SSL certificate checker: is each address's website certificate valid?
In short: Paste email addresses and see each domain's website certificate: valid, expiring, expired, wrong name or not trusted, with the issuer and days left in the CSV. Limit: Reads the domain, never the mailbox: a website certificate says nothing about a particular address.
A bulk email SSL certificate checker reads the domain after the @ in each address and makes one TLS handshake with it on port 443 to read its website certificate. Paste up to 100 unique domains a run, or 500 signed in. Each row says valid, expiring, expired, wrong name or not trusted. It checks the domain, not the mailbox. Download the CSV.
A valid website certificate doesn't make the mailbox real. Check every address.
Price: this tool is free. Checking a whole email list is from $9/mo, and the first 100 checks are free with Google, no card. Check your list free nowSee pricing
Sample result
tom@globex.example is at a domain whose website certificate expired 12 days ago.
- Address
- tom@globex.example
- Issuer
- Example CA
- Valid to
- 31 Oct 2026
What this means for you
An expired certificate can mean nobody looks after the site. It says nothing certain about the domain's mail.
- Valid, expiring, expired or wrong name
- Issuer and days left in the CSV
- Bare domain, not www
- CSV out, nothing emailed
- TLS
- Expiry
- CSV
By SimpleVerifier Team · Last updated
Got a list of company addresses and want to spot neglected domains?
- Paste it above to read each domain's website certificate, with the issuer and days left in the CSV.
- Upload or paste it at /verify. Every address gets a live mailbox check, and the first 100 email checks are free with a Google sign-in, no card.
How do I check the SSL certificates behind an email list?
- Paste email addresses, one per line, or upload a CSV. Addresses are found anywhere in the text, so a whole export works.
- Press Check certificates. Only the unique domains are sent, never the mailbox names, 10 a request: one TLS handshake on port 443 per domain, from our server, with nothing sent after it. No mail is sent.
- Read each row: Valid, Expires soon, Expired, Wrong name, Not trusted, No HTTPS or Doesn't resolve, with the reason in one line.
- Filter to the flagged addresses, download the CSV with the issuer, expiry date and days left, and hand the rest to the mailbox check.
Example
- You enter
- Four addresses:
jane@acme.example(a valid certificate),tom@globex.example(expired 12 days ago),ana@initech.example(a certificate for another name) andbo@umbrella.example(nothing on port 443). - You get
- jane: Valid, with issuer and days left. tom: Expired, the days since in the row. ana: Wrong name. bo: No HTTPS. Download the CSV.
- Limits
- Up to 100 unique domains a run without an account and 500 when signed in with Google. 10 domains a request; one TLS handshake per domain, nothing sent after it.
What does the check read?
One TLS handshake with the bare domain on port 443, using the domain as the server name. The certificate's validity dates, the names it covers and whether its chain is trusted are read from that, and the row states the result in one line. The check follows RFC 6125 for whether a certificate covers a name.
It checks the domain itself, not www., because the two can serve different certificates. Mail servers use their own certificates, which this does not read.
Why check certificates on an email list?
A company website whose certificate expired weeks ago is often a website nobody looks after, which can mean the company has slowed down or closed. It is a hint, not proof, and a domain used only for mail often has no website at all, so No HTTPS is common and means little.
A list of thousands of addresses has far fewer unique domains, so reading one certificate per domain is cheap.
What do you do with the flagged rows?
Look at Expired rows by company name before you drop them. To see which of those sites answer at all, use the bulk email website status checker, and for the whole picture of whether a company looks gone, the bulk email dead company website checker.
Before you email anyone on the rest, verify the addresses.
Who uses this tool, and for what?
- Sales teams
- Spot lead-list companies whose website certificate lapsed weeks ago.
- Agencies
- Find client-list domains whose certificate expires soon.
- Marketers
- Prioritise a list for a recheck before an import.
- Developers
- Triage a signup export for addresses at neglected domains.
What can’t this tool tell you?
- Reads the domain, never the mailbox: a website certificate says nothing about a particular address.
- Only the bare domain on port 443 is checked, not www. and not a mail server's certificate.
- A domain used only for mail often has no website, so No HTTPS is common and means little.
- Up to 100 unique domains a run without an account, 500 signed in. Free providers such as gmail.com are looked up like any domain.
Common questions
- How do I check the SSL certificates behind an email list?
- Paste the list into a bulk email SSL certificate checker like this one. It reads each address's domain and makes one TLS handshake on port 443 to read the website certificate.
- Is this bulk email SSL certificate checker free?
- Yes. It is a free tool: up to 100 unique domains a run with no account, and up to 500 a run when you sign in with Google, with no card.
- Does an expired certificate mean the mailbox is gone?
- No. It checks the domain, not the mailbox. An expired website certificate is a hint that nobody maintains the site, not a statement about its mail.
- Why does a row say No HTTPS?
- Nothing answered TLS on port 443. Many domains used only for mail run no website.
- Does it check the certificate on the mail server?
- No. It reads the website certificate on port 443 only. Mail servers use their own certificates.
- Does it send an email to the domain?
- No. It makes one TLS handshake on port 443 and sends nothing after it. It never connects to a mail server.
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
Plans from $9 a month, 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.