Bulk Seznam email checker: check a list of seznam.cz addresses at once
In short: Checks many seznam.cz, email.cz, post.cz and spoluzaci.cz addresses at once: duplicates and +tag repeats flagged, and 10 mailboxes asked live at Seznam's server. Limit: Seznam doesn't publish how its servers answer mailbox checks; the handling here is from our own checks, which can change.
A bulk Seznam email checker tests many seznam.cz, email.cz and post.cz addresses at once. Syntax, duplicates and dead domains are flagged in your browser, then the first 10 are asked live at Seznam's mail server, which rejected made-up addresses with 550 5.1.1 sorry, no such mailbox here on 12 October and 8 November 2026. A missing mailbox comes back invalid, a real one valid, an unclear answer risky.
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
By SimpleVerifier Team · Last updated
How do I check a whole list of Seznam addresses?
- Export the list as a CSV or copy the email column; Seznam rows and every other domain can go in together.
- 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 if many Seznam addresses exist?
- Paste the addresses, one per line, or a CSV column of them. Addresses at other providers are checked as normal addresses and marked.
- Press Check the Seznam addresses.
- Read the flagged rows: a typo domain, a duplicate, a +tag repeat of an earlier row, or a domain with no mail server.
- Download the clean list. Notes stay on it; only rows that fail a check come off.
- The first 10 go to Seznam's mail server for a live answer. Sign in with Google to check the rest with 100 free email checks.
Example
- You enter
- 6 addresses:
jane.doe@seznam.cz,jane.doe+deals@seznam.cz,Jane.Doe@seznam.cz, an email.cz, a post.cz and a company address. - You get
Jane.Doe@seznam.czis marked as a duplicate of row 1 and comes off;jane.doe+deals@seznam.czis marked as row 1 plus a +tag and kept. The live check asks Seznam about the Seznam rows first, and a missing mailbox comes back invalid.- Limits
- The browser pass covers the first 5,000 rows; only domains leave your device. 10 live checks a day without an account, then the free checks with a Google sign-in.
Can you check if Seznam addresses exist in bulk?
Yes. On 8 November 2026 seznam.cz, email.cz, post.cz and spoluzaci.cz all published mx1.seznam.cz and mx2.seznam.cz as their mail servers, and Seznam rejected made-up addresses at RCPT TO on 12 October and again on 8 November. A result for a Seznam row therefore comes from Seznam's server.
The free page asks about 10 mailboxes live. A whole list goes through the bulk verifier, where Seznam rows get the same check.
Why do Seznam mailboxes disappear?
The Email.cz terms let Seznam block a mailbox that was never used in its first 14 days, or one its owner hasn't logged into for more than six months. A valid result here means the mailbox exists today, so re-check a Czech list at least twice a year.
Seznam's guidance for bulk senders asks for double opt-in and for non-existent and inactive contacts to be deleted.
What does the bulk Seznam check do to my list?
The pass over the whole list runs in your browser: syntax, duplicates, typo domains and role addresses. Only the unique domains are sent out, to look up mail servers and the disposable list. Rows at seznam.cz, email.cz, post.cz and spoluzaci.cz are matched by the part after the @, so an address at any other domain is checked as a normal address and marked as another provider.
Then the first 10 addresses, Seznam rows first, are asked live at the mail server without sending anything. Sign in with Google to check the rest with 100 free email checks. For one address with full notes, use the Seznam checker.
What does each check catch on a Seznam list?
| Check | Can we confirm it? | Result when it fails |
|---|---|---|
| Syntax and duplicates | Yes, in your browser | Bad syntax comes off; a duplicate is marked |
| Domain and mail server (MX) | Yes, from DNS | No mail server comes off |
| Disposable or role address | Yes | Disposable comes off; a role address is marked |
| The mailbox exists | Yes: Seznam answers at RCPT TO (550 5.1.1 sorry, no such mailbox here) | Invalid, "Mailbox not found"; an unclear reply is risky |
| Someone reads the inbox | No checker can | Use opens, replies or a small first send |
Mailbox behaviour as measured on seznam.cz on 12 October and 8 November 2026.
Who uses this tool, and for what?
- Czech shops and newsletters
- Drop blocked or never-used seznam.cz mailboxes before a campaign.
- Lead buyers
- Check the Czech webmail rows of a list before importing it.
- List owners
- Find repeated rows and +tag copies before counting your audience.
What can’t this tool tell you?
- Seznam doesn't publish how its servers answer mailbox checks; the handling here is from our own checks, which can change.
- Typo-domain detection covers the big webmail domains and slips like .con, not Czech domain misspellings.
- A +tag repeat is marked as possibly the same inbox, not merged, because this page doesn't verify how Seznam treats tags.
- The live check covers 10 addresses without an account; risky results there can mean the check was cut short, so try again later.
- Valid means the mailbox exists today, not that anyone reads it.
Common questions
- Are email.cz and post.cz Seznam addresses?
- They use Seznam's mail servers: on 8 November 2026 email.cz, post.cz and spoluzaci.cz published the same mx1 and mx2.seznam.cz hosts as seznam.cz, and this page counts all four as Seznam rows.
- Does Seznam block inactive mailboxes?
- The Email.cz terms allow Seznam to block a mailbox never used in its first 14 days, or one not logged into for more than six months.
- Is there a free bulk Seznam checker?
- Yes. This page checks a whole list for syntax, duplicates, typo domains and dead domains for free, asks Seznam's server about 10 mailboxes live, and gives 100 free email checks with a Google sign-in. No card.
- Will the Seznam users know I checked their address?
- No. The check ends after the mail server answers about the mailbox, before any message content is sent, so nothing arrives in their inbox.
- What happens to the addresses on my list that aren't Seznam?
- They are checked as normal addresses and marked as another provider. The live check asks about the Seznam rows first.
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.