# Unknown subscriber

> Unknown subscriber is the carrier reason for a message to a number that no longer exists on any network: the number was disconnected, recycled or never allocated. Remove it from the list.

The operator's registers have no record of the number. Sending again will fail again, at the same cost. A rising share of unknown subscribers over successive campaigns is the clearest sign that a list needs cleaning; it is also the first thing to check when a delivery rate drops.

Unknown numbers cannot be detected at import, only by a lookup or by a first send. Removing them after each campaign is the habit that keeps lists healthy.

At SMSMeteor: unknown numbers are flagged in the report and can be removed from the list in one click; the first small send to a new list is the cheapest cleaning available.

Related terms: [Absent subscriber](https://smsmeteor.com/glossary/absent-subscriber), [HLR lookup](https://smsmeteor.com/glossary/hlr-lookup), [Delivery rate](https://smsmeteor.com/glossary/delivery-rate)

---
Source: https://smsmeteor.com/glossary/unknown-subscriber (HTML). Generated by SMSMeteor from the same data as the page. Summary of the whole site: https://smsmeteor.com/llms.txt