One of the biggest problems of the Internet is spam. Spam, also called “Unsolicited Comemrcial Email”, is based on the fact, that is basically free to send millions of mails and that there are always some people buying the advertised product. The cost for the shipment of the mails is so low, that there is still a profit, even if only a few people buy the product.
Today, mails are sent from Botnets. Botnets are thousands of hijacked computers, which are centrally controlled. Spammer can rent these botnets for a few hours or days. In a short time millions of spam-mails are sent.
Mail addresses were found by crawlers in the Internet, bought from dealers or simply guessed.
Spam itself is not dangerous, just annoying. If you use the same email address for years, it is very common that you get more then 1’000 spam mails per day. Receiving Mail without spam filter is impossible today. The spam rate is constantly over 90%.
Of course you could simply delete all unwanted mails, but that wastes a lot of time. Synchronizing your mail to a smartphone becomes a nightmare too. The useless amount of data transferred can become very costly.
In the meantime fighting spam is an own subject in the IT industry.