Bulk Email Checker for onet.pl Lists (Polish Addresses, Free)
For a Polish list, the bulk Onet email checker flags syntax, duplicates and dead domains across every row and asks Onet Poczta's server about the first 10. Sign in with Google for the free checks on the rest.
Onet rejected made-up addresses with 550 5.1.1 … User unknown on 12 October and 8 November 2026, so a missing onet.pl mailbox comes back invalid.
What the server says
On 8 November 2026 onet.pl published one MX host, mx.poczta.onet.pl. On 12 October it answered a made-up address at RCPT TO with 550 5.1.1 Recipient address rejected: User unknown, and a fresh one got the same rejection on 8 November. A rejected row is a hard bounce.
How old accounts disappear
Onet's Poczta terms (Polish, PDF) let it end the free service and delete an account after at least 12 months without a login. A deleted address can later go to another user, though not before at least 12 months after deletion. That is why a valid result means the mailbox exists today, not that it is the same person.
What Onet asks of senders
Onet's advice for bulk senders (Polish) asks for SPF, DKIM, DMARC and BIMI, a List-Unsubscribe header and double opt-in.
The by-hand way
- Filter the sheet to onet.pl.
- Remove repeats and typos.
- Test addresses one at a time with the Onet email checker.
In the tool
Paste the list, read the flags for typo domains, duplicates, +tag repeats and dead domains, download the clean list, and let the first 10 reach Onet for a live answer. Another Polish provider is covered by the bulk wp.pl checker.
What this check cannot do
- Onet doesn't publish how its servers answer mailbox checks; the handling is from our own checks, which can change.
- It can't tell whether a reissued address belongs to a new person.
- A +tag repeat is marked as possibly the same inbox, not merged.
Next: the whole list
The verify page on simpleverifier.com takes a list of any size: the first 100 checks are free with a Google sign-in, no card.
Try it now
Paste your list into the bulk Onet email checker.
Common questions
Can you check onet.pl addresses in bulk?
Yes. Onet's server rejected made-up addresses with 550 5.1.1 User unknown on 12 October and 8 November 2026, so a missing mailbox comes back invalid. The first 10 are asked live; sign in with Google for the rest.
When does Onet delete an account?
Onet Poczta's terms let it end the free service and delete an account with everything in it after at least 12 months without a login.
Can an old onet.pl address belong to someone new?
The terms say a deleted address can later go to another user, but not before at least 12 months after deletion, and some addresses may never be released.
Are wp.pl and o2.pl rows Onet rows?
No. Only onet.pl counts; wp.pl and o2.pl rows are checked as normal addresses and marked as another provider.
Does the check notify the owners?
No. It ends after the mail server answers about the mailbox, before any message content is sent.
Check your list before you send
Real mailbox checks over SMTP, and nothing is sent to the address. Sign in with Google and your first 100 email checks are free, no card. Plans for bigger lists are on the pricing page.