SendmailSendmail is a general purpose internetwork email routing facility that supports many kinds of mail-transfer and delivery methods, including the Simple Mail Transfer Protocol (SMTP) used for email transport over the Internet. A descendant of the delivermail program written by Eric Allman, Sendmail is a well-known project of the free and open source software and Unix communities. It has spread both as free software and proprietary software. Allman wrote the original ARPANET delivermail which shipped in 1979 with 4.
8-bit clean8-bit clean is an attribute of computer systems, communication channels, and other devices and software, that handle 8-bit character encodings correctly. Such encoding include the ISO/IEC 8859 series and the UTF-8 encoding of Unicode. Until the early 1990s, many programs and data transmission channels were character-oriented and treated some characters, e.g., ETX, as control characters. Other assumed a stream of seven-bit characters, with values between 0 and 127; for example, the ASCII standard used only seven bits per character, avoiding an 8-bit representation in order to save on data transmission costs.
Qmailqmail 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 in the public domain by the author. When first published, qmail was the first security-aware mail transport agent; since then, other security-aware MTAs have been published. The most popular predecessor to qmail, Sendmail, was not designed with security as a goal, and as a result has been a perennial target for attackers.
Binary-to-text encodingA binary-to-text encoding is encoding of data in plain text. More precisely, it is an encoding of binary data in a sequence of printable characters. These encodings are necessary for transmission of data when the communication channel does not allow binary data (such as email or NNTP) or is not 8-bit clean. PGP documentation () uses the term "ASCII armor" for binary-to-text encoding when referring to Base64.
Open mail relayAn open mail relay is a Simple Mail Transfer Protocol (SMTP) server configured in such a way that it allows anyone on the Internet to send e-mail through it, not just mail destined to or originating from known users. This used to be the default configuration in many mail servers; indeed, it was the way the Internet was initially set up, but open mail relays have become unpopular because of their exploitation by spammers and worms. Many relays were closed, or were placed on blacklists by other servers.
BinHexBinHex, originally short for "binary-to-hexadecimal", is a binary-to-text encoding system that was used on the classic Mac OS for sending binary files through e-mail. Originally a hexadecimal encoding, subsequent versions of BinHex are more similar to uuencode, but combined both "forks" of the Mac file system together along with extended file information. BinHexed files take up more space than the original files, but will not be corrupted by non-"8-bit clean" software.
Email encryptionEmail encryption is encryption of email messages to protect the content from being read by entities other than the intended recipients. Email encryption may also include authentication. Email is prone to the disclosure of information. Most emails are encrypted during transmission, but they are stored in clear text, making them readable by third parties such as email providers. By default, popular email services such as Gmail and Outlook do not enable end-to-end encryption.
Postfix (software)Postfix is a free and open-source mail transfer agent (MTA) that routes and delivers electronic mail. It is released under the IBM Public License 1.0 which is a free software license. Alternatively, starting with version 3.2.5, it is available under the Eclipse Public License 2.0 at the user's option. Originally written in 1997 by Wietse Venema at the IBM Thomas J. Watson Research Center in New York, and first released in December 1998, Postfix continues to be actively developed by its creator and other contributors.
Message submission agentA 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. Many MTAs perform the function of an MSA as well, but there are also programs that are specially designed as MSAs without full MTA functionality.
EximExim is a mail transfer agent (MTA) used on Unix-like operating systems. Exim is a free software distributed under the terms of the GNU General Public License, and it aims to be a general and flexible mailer with extensive facilities for checking incoming e-mail. Exim has been ported to most Unix-like systems, as well as to Microsoft Windows using the Cygwin emulation layer. Exim 4 is currently the default MTA on Debian Linux systems. Many Exim installations exist, especially within Internet service providers and universities in the United Kingdom.
