The Simple Mail Transfer Protocol (SMTP) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages. User-level email clients typically use SMTP only for sending messages to a mail server for relaying, and typically submit outgoing email to the mail server on port 587 or 465 per RFC 8314. For retrieving messages, IMAP is standard, but proprietary servers also often implement proprietary protocols, e.g., Exchange ActiveSync.
Spamming is the use of messaging systems to send multiple unsolicited messages (spam) to large numbers of recipients for the purpose of commercial advertising, for the purpose of non-commercial proselytizing, for any prohibited purpose, or simply repeatedly sending the same message to the same user. While the most widely recognized form of spam is email spam, the term is applied to similar abuses in other media: instant messaging spam, Usenet newsgroup spam, Web search engine spam, spam in blogs, wiki spam, online classified ads spam, mobile phone messaging spam, Internet forum spam, junk fax transmissions, social spam, spam mobile apps, television advertising and file sharing spam. It is named after Spam, a luncheon meat, by way of a Monty Python sketch about a restaurant that has Spam in almost every dish in which Vikings annoyingly sing "Spam" repeatedly.
A signature block is a personalized block of text automatically appended at the bottom of an email message, Usenet article, or forum post.
The Spam Prevention Early Warning System (SPEWS) was an anonymous service that maintained a list of IP address ranges belonging to internet service providers (ISPs) that host spammers and show little action to prevent their abuse of other networks' resources. It could be used by Internet sites as an additional source of information about the senders of unsolicited bulk email, better known as spam.
Various anti-spam techniques are used to prevent email spam.
Email spam, also referred to as junk email, spam mail, or simply spam, is unsolicited messages sent in bulk by email (spamming). 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.
A Joe job is a spamming technique that sends out unsolicited e-mails using spoofed sender data. Early Joe jobs aimed at tarnishing the reputation of the apparent sender or inducing the recipients to take action against them, but they are now typically used by commercial spammers to conceal the true origin of their messages and to trick recipients into opening emails apparently coming from a trusted source.
Opera Mail is the email and news client developed by Opera Software. It was an integrated component within the Opera web browser from version 2 through 12. With the release of Opera 15 in 2013, Opera Mail became a separate product and is no longer bundled with Opera. Opera Mail version 1.0 is available for OS X and Windows. It features rich text support and inline spell checking, spam filtering, a contact manager, and supports POP3 and IMAP, newsgroups, and Atom and RSS feeds.
mailto is a Uniform Resource Identifier (URI) scheme for email addresses. It is used to produce hyperlinks on websites that allow users to send an email to a specific address directly from an HTML document, without having to copy it and entering it into an email client.
A spambot is a computer program designed to assist in the sending of spam. Spambots usually create accounts and send spam messages with them. Web hosts and website operators have responded by banning spammers, leading to an ongoing struggle between them and spammers in which spammers find new ways to evade the bans and anti-spam programs, and hosts counteract these methods.
Disposable email addressing, also known as DEA or dark mail or "masked" email, refers to an approach which involves a unique email address being used for every contact, entity, or for a limited number of times or uses. The benefit is that if anyone compromises the address or utilizes it in connection with email abuse, the address owner can easily cancel it without affecting any of their other contacts.
Email harvesting or scraping is the process of obtaining lists of email addresses using various methods. Typically these are then used for bulk email or spam.
A webform, web form or HTML form on a web page allows a user to enter data that is sent to a server for processing. Forms can resemble paper or database forms because web users fill out the forms using checkboxes, radio buttons, or text fields. For example, forms can be used to enter shipping or credit card data to order a product, or can be used to retrieve search results from a search engine.
A spamtrap is a honeypot used to collect spam.
A challenge–response system is a type of that automatically sends a reply with a challenge to the (alleged) sender of an incoming e-mail. It was originally designed in 1997 by Stan Weatherby, and was called Email Verification. In this reply, the purported sender is asked to perform some action to assure delivery of the original message, which would otherwise not be delivered. The action to perform typically takes relatively little effort to do once, but great effort to perform in large numbers. This effectively filters out spammers. Challenge–response systems only need to send challenges to unknown senders. Senders that have previously performed the challenging action, or who have previously been sent e-mail(s) to, would be automatically
The term list poisoning refers to poisoning an e-mail mailing list with invalid e-mail addresses.
Backscatter is incorrectly automated bounce messages sent by mail servers, typically as a side effect of incoming spam.
Forum spam consists of posts on Internet forums that contains related or unrelated advertisements, links to malicious websites, trolling and abusive or otherwise unwanted information. Forum spam is usually posted onto message boards by automated spambots or manually with unscrupulous intentions with intent to get the spam in front of readers who would not otherwise have anything to do with it intentionally.
Since Internet users and system administrators have deployed a vast array of techniques to block, filter, or otherwise banish spam from users' mailboxes and almost all Internet service providers forbid the use of their services to send spam or to operate spam-support services, special techniques are employed to deliver spam emails. Both commercial firms and volunteers run subscriber services dedicated to blocking or filtering spam.
People tend to be a lot less bothered by spam slipping through filters into their mailbox than having desired email ("ham") blocked. Trying to balance false negatives and false positives is a critical aspect of a successful anti-spam system. Because servers are not able to block all spam, there are multiple methods for individual users to allow users to control this balance.
