In a general way, “spam mail” is considered an unsolicited, irrelevant email, sent in bulk to a list of people. Spam filters are programs created and used to identify unwanted or unsolicited emails and prevent them from reaching inboxes. Major ISPs like Google and Yahoo! have built-in spam filters and filtering processes to ensure their users are protected from “junk” email. The war between Internet Service Providers and spammers can also hurt companies and their marketing activities in the form of “false positives”; in other words, legitimate commercial emails that are mistakenly routed by spam filters to bulk folders. According to ReturnPath, about 21% of permission-based emails sent by legitimate email marketers end up in junk folders.