Some placements do not produce a profit. Every company has unprofitable placements or spam emails. Blacklist is a list or collection of them. There exist different types of Blacklists.
Every dubious IP address, that distributes spam is added to this Blacklist. Messages from these IP addresses are blocked or transferred to the spam folder. This Blacklist prevents from dangerous web pages, viruses or malware.
Learn more about whitelist, which is opposite of the blacklist.
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