Spam is unsolicited email communication, usually of a marketing nature. A large percentage of email communication consists of spam messages.
Due to the high volume of spam, email would practically be unusable if not for the invention of advanced spam filters.
The high volume of spam an email user receives results from the low cost of sending an email. Spammers are able to send large volumes of email at very little cost to them — the actual sending of the spam email is completely free. The only costs usually associated with spamming come from the purchasing of email addresses.
One of the major obstacles that spammers face is bypassing spam filters. Even without spam filters, it typically takes thousands of unsolicited emails to get one response. However, with spam filters, the number of responses the spammer receives will likely be much lower, because many recipients do not even see spam in the first place.
Some spam filters increase the extent to which they filter out email addresses. However, spam filters that are too overzealous when filtering out email addresses are more likely to accidentally place legitimate email in the spam folder.
Those who want to receive fewer spam emails can start by not posting their email addresses on any website. Since many spammers rely on bots to search through the Web in search of email addresses, email addresses listed on websites have a high likelihood of attracting spammers.
If an email owner is not sure whether he or she has an email address listed on a website, the best option is to search for the email address using a search engine. The user can then ask the website to take the email address down.
Another option is to sign up for a free email service and use that email address when signing up for websites. Most websites require that users provide an email address when sign up for an account.
However, some websites will sell these email addresses to spammers. Using a free email address will allow the user to sign up for an account and then simply never visit the inbox.