Optimum is an US regional ISP mailbox (Altice). Across 38,181 Optimum addresses verified by BounceZero between April and October 2026, 92.9% were invalid, 0.0% catch-all, 0.8% unknown and 6.0% confirmed valid. The invalid share is far above the business average.
Every Optimum address BounceZero verified for customers between April and October 2026, beside the corpus benchmarks. The remainder of each row to 100% is risky and role results.
| Segment | Addresses | Invalid | Catch-all | Unknown | Confirmed valid |
|---|---|---|---|---|---|
| Optimum | 38,181 | 92.9% | 0.0% | 0.8% | 6.0% |
| All non-freemail domains (business and ISP) | 6,514,884 | 14.5% | 2.3% | 27.0% | 32.6% |
| Business domains only (consumer ISP and freemail excluded) | 1,269,919 | 22.9% | 9.4% | 22.5% | 40.3% |
| All freemail | 1,415,154 | 17.6% | 1.1% | 2.1% | 74.0% |
| All .net addresses | 1,252,193 | 17.6% | 0.6% | 28.8% | 19.9% |
Non-freemail includes consumer ISP mailboxes; a business-only cut is on the benchmarks page. Method and every other cut: Lead List Quality Benchmarks 2026. Risky and role on the Optimum row: 0.3%.
Optimum answers probes decisively and more than nine in ten addresses verify as invalid. The provider closed large numbers of legacy mailboxes during platform migrations, so almost any optimum.net address on a list is a dead one.
Optimum is the consumer brand of Altice USA in the New York metropolitan area. During platform migrations the provider closed large numbers of legacy mailboxes, and the gateway now rejects them outright, which is why the invalid share is above ninety percent. Lists that still carry optimum.net addresses in volume were compiled from records that predate the migration and should be treated as stale throughout.
On confirmed-invalid rate, Optimum ranks 1 of 29 providers in the corpus, ahead of Hotmail Australia at 92.7%.
On unknown rate, Optimum ranks 24 of 29 providers in the corpus, just behind Alice (TIM) at 2.6%, ahead of Live.nl at 0.7%.
On confirmed-valid share, Optimum ranks 23 of 29 providers in the corpus, just behind AOL at 11.0%, ahead of AT&T at 5.8%.
How to read these rates: they are BounceZero's probe outcomes on customer lists over April to October 2026, not a census of Optimum mailboxes. Unknown and catch-all measure what verification could not confirm, which depends on the provider's gateway policy during the window as much as on the addresses. The lists are the ones customers chose to upload, so segments dominated by a few large uploads carry their age and source. Method and limitations: benchmarks page.
Unknown is a rounding error on Optimum at 0.8%; the gateway gives a clear answer and the verdict stands.
Optimum fails at 92.9%, which is 6.4 times the business-list rate; the segment is a relic and so, probably, is the list around it.
Catch-all is negligible on Optimum (0.0%); when this provider does return valid, the mailbox accepted the probe itself rather than a blanket accept.
Confirmed valid is 6.0%. Send to that slice from the primary domain and treat the rest of the Optimum segment as unreachable by cold email.
Expect near-total loss. The domain is a reliable marker that a list was compiled from records more than a few years old.
Role addresses such as info@ and sales@ make up 0.0% of Optimum addresses in the corpus. Role addresses are rare here, as expected for a mailbox provider.
92.9% of 38,181 Optimum addresses verified by BounceZero between April and October 2026 were confirmed invalid, against 14.5% across non-freemail domains and 17.6% across freemail.
0.8%. Unknown means the mailbox could not be confirmed either way, usually because the gateway deferred the probe. BounceZero refunds unknown results; on Optimum it is rare enough to re-check once and move on.
Not in practice: 0.0% of Optimum addresses returned catch-all, so a valid verdict means the mailbox exists.
6.0% confirmed valid at verification time. Keep bounces under 2% and complaints under 0.3% on the send, and re-verify the segment before every send.
Upload the file and see valid, invalid, catch-all and unknown per row, with the Optimum segment against this benchmark. 100 free checks a month, unknowns refunded.
Ayoub built BounceZero's 5-stage validation pipeline, its dedicated BGP-announced IP infrastructure, and the Patroni HA PostgreSQL cluster behind every verification. Previously built high-volume email delivery infrastructure. Trained at 1337 Benguerir (École 42 network, 2019). Open-source: bgp_analyzer.
Invalid, catch-all and unknown rates per email provider and country domain, 2026
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56,401 .org addresses verified April to October 2026
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