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Since spam occurs primarily because it is so cheap to send, a proposed set of solutions require that senders pay some cost in order to send spam, making it prohibitively expensive for spammers.
Some gatekeeper would sell electronic stamps and keep the proceeds. Or a micropayment, such as electronic money would be paid by the sender to the recipient or their ISP, or some other gatekeeper.
Proof-of-work systems such as hashcash and Penny Black require that a sender pay a computational cost by performing a calculation that the receiver can later verify. Verification must be much faster than performing the calculation, so that the computation slows down a sender but does not significantly impact a receiver. The point is to slow down machines that send most of spam—often millions and millions of them. While every user that wants to send email to a moderate number of recipients suffers just a few seconds' delay, sending millions of emails would take an unaffordable amount of time. This approach suffers when sender maintains a computation farm of their own or from zombies.
As a refinement to stamp systems is the method of requiring that a micropayment only be made (or some other form of penalty imposed) if the recipient considers the email to be abusive. This addresses the principal objection to stamp systems: popular free legitimate mailing list hosts would be unable to continue to provide their services if they had to pay postage for every message they sent.
In 2004 Bill Gates announced that Microsoft was working on a solution requiring so-called “unknown senders”, i.e. senders not on the Accepted List of the recipient to post “the electronic equivalent of a” stamp whose value would be lost to the sender only if the recipient disapproves of the email. [1] Gates said that Microsoft favors other solutions in the short-term, but would rely on the contingent payment solution to solve the spam problem over the longer run. Microsoft, AOL as well as Yahoo! have recently[ when? ] introduced systems that allow commercial senders to avoid filters if they obtain a paid or pre-paid certificate or certification, which is lost to the sender if recipients complain.
This approach suffers when a user initially signs up for a legitimate mailing list, but then later decides they do not want to receive the e-mail any further. Lazy users will simply click the "This is Spam" button on their e-mail client, rather than going through the formal unsubscription process that is detailed at the bottom of each message. The end-user gets the same effect either way, but without realizing the consequences that the list host may now face. However, companies now implementing the penalty approach when certifying (and withdrawing certification from) commercial senders have learned to account for this problem by setting appropriate complaint thresholds.
The intent of all such "sender-at-risk" solutions, which impose a significant cost to the sender only if the recipient rejects the message subsequent to receiving the email, is to deter spam by making it economically prohibitive to send unwanted email messages, while allowing legitimate emailers to send messages at little or no expense.
Anti-spam activist Daniel Balsam attempts to make spamming less profitable by bringing lawsuits against spammers. [2] While this approach is financially sustainable for the activist, it is questionable whether it actually reduces spam, either for the activist or for anyone else. [3]
Electronic mail is a method of transmitting and receiving messages using electronic devices. It was conceived in the late–20th century as the digital version of, or counterpart to, mail. Email is a ubiquitous and very widely used communication medium; in current use, an email address is often treated as a basic and necessary part of many processes in business, commerce, government, education, entertainment, and other spheres of daily life in most countries.
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.
Various anti-spam techniques are used to prevent email spam.
The Controlling the Assault of Non-Solicited Pornography And Marketing (CAN-SPAM) Act of 2003 is a law passed in 2003 establishing the United States' first national standards for the sending of commercial e-mail. The law requires the Federal Trade Commission (FTC) to enforce its provisions. Introduced by Republican Conrad Burns, the act passed both the House and Senate during the 108th United States Congress and was signed into law by President George W. Bush in December 2003 and was enacted on January 1, 2004.
Mobile phone spam is a form of spam, directed at the text messaging or other communications services of mobile phones or smartphones. As the popularity of mobile phones surged in the early 2000s, frequent users of text messaging began to see an increase in the number of unsolicited commercial advertisements being sent to their telephones through text messaging. This can be particularly annoying for the recipient because, unlike in email, some recipients may be charged a fee for every message received, including spam. Mobile phone spam is generally less pervasive than email spam, where in 2010 around 90% of email is spam. The amount of mobile spam varies widely from region to region. In North America, mobile spam steadily increased after 2008 and accounted for half of all mobile phone traffic by 2019. In parts of Asia up to 30% of messages were spam in 2012.
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.
Sender Policy Framework (SPF) is an email authentication method which ensures the sending mail server is authorized to originate mail from the email sender's domain. This authentication only applies to the email sender listed in the "envelope from" field during the initial SMTP connection. If the email is bounced, a message is sent to this address, and for downstream transmission it typically appears in the "Return-Path" header. To authenticate the email address which is actually visible to recipients on the "From:" line, other technologies such as DMARC must be used. Forgery of this address is known as email spoofing, and is often used in phishing and email spam.
Hashcash is a proof-of-work system used to limit email spam and denial-of-service attacks. Hashcash was proposed in 1997 by Adam Back and described more formally in Back's 2002 paper "Hashcash - A Denial of Service Counter-Measure". In Hashcash the client has to concatenate a random number with a string several times and hash this new string. It then has to do so over and over until a hash beginning with a certain amount of zeros is found.
Greylisting is a method of defending e-mail users against spam. A mail transfer agent (MTA) using greylisting will "temporarily reject" any email from a sender it does not recognize. If the mail is legitimate, the originating server will try again after a delay, and if sufficient time has elapsed, the email will be accepted.
The Penny Black Project is a Microsoft Research project that tries to find effective and practical ways of fighting spam. Because identifying spams consumes a recipient's time, the idea is to make the sender of emails "pay" a certain amount for sending them. The currency or the mode of payment could be CPU cycles, Turing tests or memory cycles. Such a payment would limit spammers' ability to send out large quantities of emails quickly.
A bounce message or just "bounce" is an automated message from an email system, informing the sender of a previous message that the message has not been delivered. The original message is said to have "bounced".
Email marketing is the act of sending a commercial message, typically to a group of people, using email. In its broadest sense, every email sent to a potential or current customer could be considered email marketing. It involves using email to send advertisements, request business, or solicit sales or donations. Email marketing strategies commonly seek to achieve one or more of three primary objectives: build loyalty, trust, or brand awareness. The term usually refers to sending email messages with the purpose of enhancing a merchant's relationship with current or previous customers, encouraging customer loyalty and repeat business, acquiring new customers or convincing current customers to purchase something immediately, and sharing third-party ads.
A message submission agent (MSA), or mail submission agent, is a computer program or software agent that receives electronic mail messages from a mail user agent (MUA) and cooperates with a mail transfer agent (MTA) for delivery of the mail. It uses ESMTP, a variant of the Simple Mail Transfer Protocol (SMTP), as specified in RFC 6409.
Emailtracking is a method for monitoring whether the email message is read by the intended recipient. Most tracking technologies use some form of digitally time-stamped record to reveal the exact time and date when an email is received or opened, as well as the IP address of the recipient.
Memory bound refers to a situation in which the time to complete a given computational problem is decided primarily by the amount of free memory required to hold the working data. This is in contrast to algorithms that are compute-bound, where the number of elementary computation steps is the deciding factor.
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 receive a challenge.
DomainKeys Identified Mail (DKIM) is an email authentication method designed to detect forged sender addresses in email, a technique often used in phishing and email spam.
An email alias is simply a forwarding email address. The term alias expansion is sometimes used to indicate a specific mode of email forwarding, thereby implying a more generic meaning of the term email alias as an address that is forwarded in a simplistic fashion.
Backscatter is incorrectly automated bounce messages sent by mail servers, typically as a side effect of incoming spam.
SmartScreen is a cloud-based anti-phishing and anti-malware component included in several Microsoft products: