Seznam email checker: seznam.cz, email.cz and post.cz
In short: Asks Seznam's own mail servers whether a seznam.cz, email.cz, post.cz or spoluzaci.cz mailbox exists, without sending anything, after syntax, domain, disposable and role checks. Limit: A valid result shows Seznam accepted the mailbox today, not that anyone reads it.
To check if a Seznam address exists, enter it here. The checker asks Seznam's mail server about the mailbox at RCPT TO and disconnects before sending. Seznam rejected made-up addresses with 550 5.1.1 sorry, no such mailbox here on 12 October and 8 November 2026, so a missing mailbox comes back invalid and an accepted one valid; anything unconfirmed stays 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
Tuned for seznam.cz, email.cz, post.cz, spoluzaci.cz. Five checks a minute, no account needed. Nothing is sent to the address — we ask its mail server whether the mailbox exists, then disconnect.
What can a check confirm at Seznam, and what did we measure there? Can you verify a Seznam address?
Sample result
[email protected] doesn't exist: Seznam's server rejected it.
- [email protected]
- Reason
- Mailbox not found
- Mailbox check
- SMTP, nothing sent
What this means for you
Invalid means remove it; a real mailbox would come back valid.
- Asks Seznam's server at RCPT TO
- Catch-all test with a random address first
- Catches typo domains with no mail server
- Flags disposable and role addresses
- Seznam
- seznam.cz
- email.cz
By SimpleVerifier Team · Last updated
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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. The first 100 email checks are free with a Google sign-in, no card.
- For every list after that, Pro includes unlimited email verification. Fair use: the first 100,000 checks a month at full speed, then slower, never cut off.
How do I check a Seznam email address?
- Type or paste one address, such as
[email protected],[email protected]or[email protected]. - Press Check. The tool checks the syntax and domain, asks Seznam's server about a random address that can't exist, then about yours, and disconnects before anything is sent.
- Read the verdict: valid means Seznam accepted the mailbox and rejected the made-up one, invalid means it said there is no such mailbox, risky means the check didn't get a clear answer.
- If it comes back risky, check again later before you drop the address.
Example
- You enter
- One address:
[email protected]. - You get
- Valid when Seznam accepts the mailbox after rejecting a random address; invalid ("Mailbox not found") when it answers
550 5.1.1 sorry, no such mailbox here; risky only when the check gets no clear answer. - Limits
- Five checks a minute per IP address, one address at a time, no account needed.
Can you check if a Seznam email address exists?
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. On 12 October 2026 Seznam answered a made-up address at RCPT TO with 550 5.1.1 sorry, no such mailbox here, and a fresh made-up address was rejected again through this checker on 8 November.
A missing Seznam mailbox therefore comes back invalid ("Mailbox not found"), and one Seznam accepts after rejecting a random address comes back valid. The Seznam provider page has the live DNS snapshot.
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. Sign-ups that gave a fresh @seznam.cz address and never engaged are worth checking before a campaign.
Seznam's guidance for bulk senders asks for double opt-in and for non-existent and inactive contacts to be deleted, and its authentication page says valid SPF and DKIM are required for delivery.
Can I check a whole list of Czech addresses?
Yes. Sign in and use the bulk verifier for a CSV or a pasted list; Seznam rows get the same mailbox check as here, alongside Gmail and everything else. Because Seznam can block mailboxes after six idle months, re-check a Czech list at least twice a year.
For one Gmail address, the Gmail address checker works the same way, and the email checker handles any other domain.
What can this checker confirm at Seznam?
Each row is something the check runs on a Seznam address, and the result you can get from it.
| Check | Can we confirm it? | Result when it fails |
|---|---|---|
| Syntax (the address is written correctly) | Yes | Invalid |
| Domain and mail server (MX) | Yes | Invalid, with a typo suggestion where one fits |
| Disposable or role address | Yes | Invalid (disposable) or risky (role) |
| The mailbox exists | Yes: Seznam answers at RCPT TO (550 5.1.1 no such mailbox) | Invalid, "Mailbox not found" |
| A temporary reply or timeout | No answer to read | Risky, worth checking again later |
| Someone reads the inbox | No checker can | Use opens, replies or a small first send |
Our checking server offered a made-up address and disconnected without sending, on 12 or 13 October 2026 and again through this checker on 8 November 2026.
Who uses this tool, and for what?
- Czech shops and newsletters
- Drop blocked or never-used seznam.cz mailboxes before Seznam reads them as poor list hygiene.
- Support teams
- Catch a mistyped address, or a typo domain like seznam.cy, before you reply.
- Lead buyers
- Confirm a handful of Czech webmail contacts before importing a list.
What can’t this tool tell you?
- A valid result shows Seznam accepted the mailbox today, not that anyone reads it.
- A temporary reply or a refused connection comes back risky, not invalid.
- Seznam doesn't publish how its servers answer mailbox checks; the handling here is from our own checks, which can change.
- One address at a time, five a minute.
Common questions
- How do I check if a seznam.cz address is valid?
- Enter it here. The checker confirms the syntax and mail servers, then asks Seznam's server about the mailbox without sending. Seznam rejects addresses that don't exist, so a missing mailbox comes back invalid.
- 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 checker covers all four.
- 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.
- What does sorry, no such mailbox here mean?
- Seznam's server has no mailbox by that name. It is a permanent rejection (550 5.1.1), so treat it as a hard bounce and remove the address.
- Is this checker free?
- Yes, five checks a minute with no account. For a whole list, sign in with Google for 100 free email checks, no card, or use a monthly plan.
Sources
That was one address. Most people have a list.
The free checker does five addresses a minute, one at a time — fine for spot-checking, useless for a CSV of 40,000.
- Upload a CSV up to 100,000 rows
- Valid, risky and invalid exported as separate files
- Repeat checks free for 14 days, no new connections
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.