Anti Spam: -

Refers to any software, hardware or process that is used to combat the proliferation of spam or to keep spam from entering a system. An ideal anti-spam system rejects messages which are both bulk and unsolicited, letting pass those messages which are of specific personal relevance to the recipient (not "bulk"), and those which the recipient has expressly requested (not "unsolicited"). When phrased in these terms, spam filtering is obviously a task for a well-informed intelligent agent of immense sophistication—quite beyond our current ability to construct. Anything less is a weak approximation at best.