Spam is the abuse of electronic messaging systems to indiscriminately send unsolicited bulk messages. Spamming remains economically viable because advertisers have no operating costs beyond the management of their mailing lists, and it is difficult to hold senders accountable for their mass mailings.

Because the barrier to entry is so low, spammers are numerous, and the volume of unsolicited mail has become very high. The costs, such as lost productivity and fraud, are borne by the public and by Internet service providers, which have been forced to add extra capacity to cope with the deluge.

Spamming is widely reviled, and has been the subject of legislation in many jurisdictions. Spam is almost impossible to stop completely, but it can be reduced to a less aggravating level through spam filters and legislation.