BSD, Berkeley System Distribution

A family of Unix versions developed by Bill Joy and others at the University of California at Berkeley, originally for the DEC VAX and PDP-11 computers, and subsequently ported to almost all modern general-purpose computers. BSD Unix incorporates paged virtual memory, TCP/IP networking enhancements and many other features [FOLDOC].

DKIM, Domain Keys Identified Mail

This adds a DKIM signature to each outbound email message on a system which can then be verified by recipients. Recipient SMTP servers will look up the DKIM selector of the mail, and verify that the key the mail is signed with matches the public key in DNS.

DNS, Domain Name System

This system is used to convert IP Addresses into hostnames. It is also used to determine where mail should be routed for a domain.

FTP, File Transfer Protocol

FTP used to be used to transfer large files over the internet. It is an archaic protocol.

FTPS, File Transfer Protocol Secure

FTPS is an extension to FTP that allows encryption using TLS or SSL. It is not to be confused with SFTP, which is a subsystem of SSH.

HTML, Hypertext Markup Language

A system to mark up documents. It is the most common format used for documents on the world-wide web, and is the format that web browsers display.

HTTP, Hypertext Transfer Protocol

This protocol was originally used to transfer HTML documents between machines connected to the internet. It has become the standard protocol for transferring all types of documents over the world-wide web.

IMAP, Internet Message Access Protocol

The Internet Message Access Protocol (IMAP) is one of the two most prevalent Internet standard protocols for e-mail retrieval, the other being the Post Office Protocol (POP). Virtually all modern e-mail clients and mail servers support both protocols as a means of transferring e-mail messages from a server.

IP, Internet Protocol

The network layer for the TCP/IP protocol suite widely used on Ethernet networks, defined in STD 5, RFC 791. IP is a connectionless, best-effort packet switching protocol. It provides packet routing, fragmentation and re-assembly through the data link layer.

+ IPv4 is the version in widespread use and IPv6 was just beginning to come into use in 2000 but was still not widespread by 2008 [FOLDOC].

IP Address

IP addresses come in two flavours, reflecting the two versions of IP used.

+ An IPv4 address is a 32 bit number generally represented as a dotted quad e.g. There is a limit of just under 4.3 billion IPv4 addresses, which is slowly being reached, which necessitated the invention of IPv6.

+ An IPv6 address is a 128 bit number, generally represented as a hexadecimal number, split into nibbles of up to four digits, separated by colons, e.g. 2001:41c8:12::34. There are up to 2128 or 3 × 1038 addresses available in IPv6.

ISP, Internet Service Provider

A company which provides other companies or individuals with access to, or presence on, the Internet. Most ISPs are also Internet Access Providers; extra services include help with design, creation and administration of World-Wide Web sites, training and administration of intranets and domain name registration [FOLDOC].


ManageSieve is a protocol that is allows Sieve filters to be managed remotely, testing any filters before allowing them to be used.

MTA, Mail Transfer Agent

A mail transfer agent is a computer process or software agent that transfers electronic mail messages from one computer to another, in single hop application-level transactions. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol.

MUC, Multi User Chat

A Multi User Chat is a feature of XMPP allowing many users to converse in the same window. This is often used to ease communication between groups in different offices, and for the sake of ease can be thought of as the point at which mailing lists and instant messages meet.

NTP, Network Time Protocol

A protocol built on top of TCP/IP that assures accurate local timekeeping with reference to radio, atomic or other clocks located on the Internet. This protocol is capable of synchronising distributed clocks within milliseconds over long time periods.[FOLDOC].


PHP is a widely-used general-purpose scripting language that is especially suited for Web development and can be embedded into HTML. [PHPNET]

POP3, Post Office Protocol 3

Version 3 of the Post Office Protocol. POP3 is defined in RFC 1081, written in November 1988 by Marshall Rose, which is based on RFC 918 (since revised as RFC 937). POP3 allows a client computer to retrieve electronic mail from a POP3 server via a (temporary) TCP/IP or other[?] connection. It does not provide for sending mail, which is assumed to be done via SMTP or some other method [FOLDOC].

Secure File Transfer Protocol, SFTP

SFTP is a file transfer protocol which involves using an SSH server to manage the file uploads. It is secure in the sense that file contents are encrypted during transfer, and that plain-text passwords are never sent over the internet. SFTP is the logical successor to FTP, which is less secure, and more complex to firewall.


Sieve is a language that can be used to filter email messages. It is a powerful language that provides a safe environment for filtering to occur during mail delivery, allowing messages to be delivered directly into mailboxes configured by the user.

SMTP, Simple Mail Transfer Protocol

A protocol defined in STD 10, RFC 821, used to transfer electronic mail between computers, usually over Ethernet. It is a server to server protocol, so other protocols are used to access the messages [FOLDOC].

SPF, Sender Policy Framework

An anti-spam measure designed to let domain administrators choose how mail sent on their domain’s behalf will be treated by recipients, which can help send spoofed mail to spam and protect your domain’s reputation.

SSH, Secure Shell

A Unix shell program for logging into, and executing commands on, a remote computer. ssh is intended to replace rlogin and rsh, and provide secure encrypted communications between two untrusted hosts over an insecure network. X11 connections and arbitrary TCP/IP ports can also be forwarded over the secure channel [FOLDOC].

SSL, Secure Sockets Layer

A protocol designed by Netscape Communications Corporation to provide secure communications over the Internet using asymmetric key encryption. SSL is layered beneath application protocols such as HTTP, SMTP, Telnet, FTP, Gopher and NNTP and is layered above the connection protocol TCP/IP. It is used by the HTTPS access method [FOLDOC].

TCP, Transmission Control Protocol

The most common transport layer protocol used on Ethernet and the Internet. It was developed by DARPA.

TCP is the connection-oriented protocol built on top of Internet Protocol (IP) and is nearly always seen in the combination TCP/IP (TCP over IP). It adds reliable communication and flow-control and provides full-duplex, process-to-process connections.

TCP is defined in STD 7 and RFC 793 [FOLDOC].

TLS, Transport Layer Security

A protocol designed to allow client/server applications to communicate over the Internet without eavesdropping, tampering, or message forgery.

TLS is defined in RFC 2246 [FOLDOC].

UDP, User Datagram Protocol

Internet standard network layer, transport layer and session layer protocols which provide simple but unreliable datagram services. UDP is defined in STD 6, RFC 768. It adds a checksum and additional process-to-process addressing information [to what?]. UDP is a connectionless protocol which, like TCP, is layered on top of IP.

UDP neither guarantees delivery nor does it require a connection. As a result it is lightweight and efficient, but all error processing and retransmission must be taken care of by the application program [FOLDOC].

URL, Uniform Resource Locator

A Uniform Resource Locator (URL) is a Uniform Resource Identifier (URI) that specifies where an identified resource is available and the mechanism for retrieving it. In popular usage and in many technical documents and verbal discussions it is often incorrectly used as a synonym for URI. The best-known example of a URL is the "address" of a web page e.g. [WIKIPEDIA_URL].

XMPP, Extensible Messaging and Presence Protocol

A protocol enabling instant messaging, contact list maintenance, and presence information. Addresses usually take the same form as an email address, eg, user@domain.tld. Various common extensions exist, including file transfer, voice and video (Jingle), service discovery, and multi user chat. Federation is another key feature of XMPP, which allows any user of XMPP to contact any other user, provided they are able to connect that user’s XMPP server. XMPP is not limited to chat, but can also be used to deliver push notifications, file sharing, and identity services.