Spam refers to unsolicited email you don’t want. The most obvious examples of spam are unsolicited commercial emails, such as ads for porn, drugs, or body enhancement products.
There are two significant qualifications to spam:
Spam is tricky. Some email programs and services automatically filter spam based on common key words, the number of people the message is being sent to, or the sender’s reputation. Some also allow you to flag messages as spam.
Unfortunately, any email that people don’t want runs the risk of being marked as spam. If an email newsletter that you signed up for changes its focus into something you don’t want, it might legitimately be considered spam.
The name comes from a Monty Python sketch in which the name of the canned pork product Spam is ubiquitous, unavoidable, and repetitive. Email spam has steadily grown since the early 1990s, and by 2014 was estimated to account for around 90% of total email traffic.
The legal definition and status of spam varies from one jurisdiction to another, but nowhere have laws and lawsuits been particularly successful in stemming spam.
Most email spam messages are commercial in nature. Whether commercial or not, many are not only annoying as a form of attention theft, but also dangerous because they may contain links that lead to phishing web sites or sites that are hosting malware or include malware as file attachments.
Spammers collect email addresses from chat rooms, websites, customer lists, newsgroups, and viruses that harvest users' address books. These collected email addresses are sometimes also sold to other spammers.