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

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.