> ## Documentation Index
> Fetch the complete documentation index at: https://docs.hub2.io/llms.txt
> Use this file to discover all available pages before exploring further.

# MSISDN - Blacklist

<Note>
  The blacklist is implemented at HUB2 level, not at provider level, although providers can integrate similar mechanisms.
</Note>

Some MSISDN can be blacklisted.

If failed transfers **to a number** are detected, and these failures are recurrent within a short time interval, then the number will be blocked.

As soon as **5 failures are detected over a period of 60 minutes**, the MSISDN will be blacklisted and blocked.

## Unblocking

A MSISDN is automatically unblocked after 7 days.