How to Clean a List With optonline.net and optimum.net Emails
Optimum addresses on an old list are a shrinking pool, and the bulk Optimum email checker shows which survive: it flags syntax, duplicates and dead domains for the whole list, then asks Optimum's server about the first 10. Sign in with Google to check the rest with free credits.
Optimum's server rejected made-up optonline.net addresses with 550 … User unknown on 13 October and 8 November 2026, so a missing mailbox comes back invalid.
Why the pool only shrinks
Optimum's email FAQ says an inbox and all its content are deleted after 90 days of email account inactivity, and every address on an account is deleted within 90 days of the Internet service being disconnected. The same FAQ says Optimum stopped letting customers create new Optimum email accounts on 4 May 2021. Any optonline.net row on your list is at least that old.
Where the answer comes from
On 8 November 2026 optonline.net and optimum.net both published one MX host, mx.altice.prod.cloud.openwave.ai. On 13 October it answered a made-up optonline.net address with 550 RCPT TO:<…@optonline.net> User unknown, and a fresh one got the same rejection on 8 November.
The by-hand way
- Filter the sheet to optonline.net and optimum.net.
- Remove repeats and obvious typos.
- Test addresses one at a time with the Optimum email checker.
In the tool
Paste the list or a CSV column, read the flags, download the clean list, and let the first 10 reach Optimum's server for a live answer.
What this check cannot do
- Optimum doesn't publish how its servers answer mailbox checks; the handling is from our own checks, which can change.
- A +tag repeat is marked as possibly the same inbox, not merged.
- Valid means the mailbox exists today, not that anyone reads it.
Next: the whole list
The verify page on simpleverifier.com takes any list size: the first 100 checks are free with a Google sign-in, no card. For Charter's domains, see the bulk Spectrum checker.
Try it now
Paste your list into the bulk Optimum email checker.
Common questions
Can you check optonline.net addresses in bulk?
Yes. Optimum's server rejected made-up optonline.net addresses with 550 User unknown on 13 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.
Does Optimum delete inactive email accounts?
Optimum's FAQ says an inbox and all its content are deleted after 90 days of email account inactivity.
Can people still create new optonline.net addresses?
No. Optimum's FAQ says that since 4 May 2021 it no longer lets customers create new Optimum email accounts.
Is optimum.net checked as an Optimum row?
Yes. optonline.net and optimum.net published the same mail server on 8 November 2026, and both count as Optimum rows.
Does a valid result mean the inbox is used?
No. Valid means the mailbox exists today, not that anyone reads it or has logged in within 90 days.
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.