Email 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.
Within the Internet email system, a message transfer agent (MTA), mail transfer agent, or mail relay is software that transfers electronic mail messages from one computer to another using the Simple Mail Transfer Protocol. In some contexts, the alternative names mail server, mail exchanger, or MX host are used to describe an MTA.
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.
An email client, email reader or, more formally, message user agent (MUA) or mail user agent is a computer program used to access and manage a user's email.
qmail is a mail transfer agent (MTA) that runs on Unix. It was written, starting December 1995, by Daniel J. Bernstein as a more secure alternative to the popular Sendmail program. Originally license-free software, qmail's source code was later dedicated to the public domain by the author.
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.
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 authentication, or validation, is a collection of techniques aimed at providing verifiable information about the origin of email messages by validating the domain ownership of any message transfer agents (MTA) who participated in transferring and possibly modifying a message.
The Sender Rewriting Scheme (SRS) is a scheme for bypassing the Sender Policy Framework's (SPF) methods of preventing forged sender addresses. Forging a sender address is also known as email spoofing.
AS2 is a specification on how to transport structured business-to-business data securely and reliably over the Internet. Security is achieved by using digital certificates and encryption.
Variable envelope return path (VERP) is a technique used by some electronic mailing list software to enable automatic detection and removal of undeliverable e-mail addresses. It works by using a different return path for each recipient of a message.
Sieve is a programming language that can be used for email filtering. It owes its creation to the CMU Cyrus Project, creators of Cyrus IMAP server.
Email tracking or email tracker 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.
In computing, Bounce Address Tag Validation (BATV) is a method, defined in an Internet Draft, for determining whether the bounce address specified in an E-mail message is valid. It is designed to reject backscatter, that is, bounce messages to forged return addresses.
A directory harvest attack (DHA) is a technique used by spammers in an attempt to find valid/existent e-mail addresses at a domain by using brute force. The attack is usually carried out by way of a standard dictionary attack, where valid e-mail addresses are found by brute force guessing valid e-mail addresses at a domain using different permutations of common usernames. These attacks are more effective for finding e-mail addresses of companies since they are likely to have a standard format for official e-mail aliases.
Ned Freed was an IETF participant and Request for Comments author who contributed to a significant number of Internet Protocol standards, mostly related to email. He is best known as the co-inventor of email MIME attachments, with Nathaniel Borenstein.
MailChannels is a Canadian technology company that specializes in email security for businesses and internet service providers (ISPs). Founded in 2004 by Ken Simpson and headquartered in Vancouver, British Columbia, the company operates in email security and the infrastructure market. The business provides a products and services designed to safeguard email systems against spam, phishing, and other harmful content. They guarantee the dependable delivery of legitimate messages and offer a mail relay API for numerous websites.
A bounce address is an email address to which bounce messages are delivered. There are many variants of the name, none of them used universally, including return path, reverse path, envelope from, envelope sender, MAIL FROM, 5321-FROM, return address, From_, Errors-to, etc. It is not uncommon for a single document to use several of these names.
AS1 is a specification about how to transport structured business-to-business data securely and reliably over the Internet. Security is achieved by using digital certificates and encryption.
Amavis is an open-source content filter for electronic mail, implementing mail message transfer, decoding, some processing and checking, and interfacing with external content filters to provide protection against spam and viruses and other malware. It can be considered an interface between a mailer and one or more content filters.
