Terms Used In Internet Mail

The following is a list of terms that are commonly found in discussions of Internet mail and brief descriptions of the terms. If you are looking for a term that you do not find here, please send a message to phoffman@imc.org so that we can add it to the list.

RFC 2828 is a quite extensive glossary of security terms.

Most of the terms in this list relate to Internet mail in general or to cryptography. If you would like to read more about these subjects, IMC recommends the following two books:

Internet Messaging, David Strom and Marshall T. Rose, Prentice Hall, 1998, ISBN 0139786104
buy at Amazon.com buy at barnesandnoble.com

Applied Cryptography, Bruce Schneier, John Wiley & Sons, 1995, ISBN 0471117099
buy at Amazon.com buy at barnesandnoble.com

Term Definition Reference
ASN.1 Abstract Syntax Notation (1). A method for describing data that is used in many other standards. CCITT, Recommendation X.208, "Specification of Abstract Syntax Notation One (ASN.1)"
CAST A cryptographic encryption algorithm that is an optional part of some standards. RFC 2144
clear-signed message A digitally signed S/MIME or PGP message in which the content of the message is readable even if the signature is not. RFC 1847
client, mail A program for viewing mail. Mail clients usually also retrieve mail from message stores using either the POP or IMAP protocols, although some mail clients read mail directly from disk. Mail clients are usually controlled by people, but some mail client programs are automated processes.
CMS Cryptographic Message Syntax. The internal format of an S/MIME message. RFC 2630
cryptography The study and practice of keeping data secure. Two common applications of cryptography are privacy (preventing unauthorized viewing of data) and authentication (proving one's identity to access data or as the source of a message). Cryptography links kept at Counterpane Systems
DES Data Encryption Standard. A cryptographic encryption algorithm that is part of many standards. American National Standards Institute, ANSI X3.106, "American National Standard for Information Systems - Data Link Encryption"
Diffie-Hellman A cryptographic key-exchange algorithm that is part of many standards. See also X9.42.
digital signature A method for proving that the holder of a private key is the originator of a message
DSS Digital Signature Standard. A cryptographic signature algorithm that is part of many standards. Also called DSA (Digital Signature Algorithm). National Institute of Standards and Technology, FIPS Pub 186: Digital Signature Standard.
ESMTP Extended Simple Mail Transfer Protocol. An extension to SMTP that gives a framework for additional extensions. RFC 1869
ETRN An ESMTP service extension for starting a remote message queue, such as for mail servers that are normally not connected to the Internet. RFC 1985
FAQ Frequently Asked Question. Usually, this is a document that lists frequently asked questions on a particular topic and gives answers to the questions.
i18n Abbreviation for "internationalization". IMC's mail internationalization information
IAB Internet Architecture Board. The body that helps define the overall architecture and design of Internet protocols. The IAB is the technical advisory group of the ISOC. http://www.iab.org/iab/
iCalendar A format for calendaring and scheduling information. The term iCalendar generally refers to the protocols associated with the iCalendar format, such as the methods to exchange iCalendar objects. http://www.imc.org/ietf-calendar/
IESG Internet Engineering Steering Group. The group who oversees the IETF working group process and determines which proposals become standards. http://www.ietf.org/iesg.html
IETF Internet Engineering Task Force. The main organization that creates protocol standards for the Internet. http://www.ietf.org/
IMAP, IMAP4 Internet Message Access Protocol. A method for mail clients to retrieve mail from a message store. IMAP is newer and has more features than the more popular POP protocol. RFC 2060
Internet Draft A document that is offered for review to the IETF. IMC's list of mail standards and drafts
IMC Internet Mail Consortium. The trade group for the Internet mail industry. http://www.imc.org/
ISOC Internet Society. The longest-standing organization promoting the use of the Internet. http://www.isoc.org/
LDAP Lightweight Directory Access Protocol. A simpler protocol for directory access than X.500. RFC 2251
mailing list A system for distributing messages to many people at once. A simple mailing list is a set of names that a single message is distributed to. A typical mailing list processor is a program that allows people to subscribe and unsubscribe from a list as well as managing the sending of messages to the lists' subscribers.
MAPI Messaging Applications Programming Interface. A proprietary interface to client mail servers.
message store The location where messages that are received by an SMTP server are held, waiting for mail clients to retrieve them. Message stores are usually just files on a hard disk, although some are databases.
MHTML MIME-enhanced HTML. A method for sending aggregated HTML documents (such as ones with images) in a single MIME message. RFC 2110
MIME Multipurpose Internet Mail Extensions. A structured format for messages which allows a single message to contain many parts. RFC 2045
MOSS MIME Object Security Services. A protocol for exchanging digitally signed and/or encrypted mail. that never gained much use. RFC 1848
MTA Mail Transfer Agent. A server running the SMTP protocol.
MUA Mail User Agent. See client, mail.
multipart A type of MIME message that contains more than one part. RFC 2046
OpenPGP A newer version of PGP that was created in the IETF. RFC 2440 and IMC's discussion of S/MIME and OpenPGP
PEM Privacy Enhanced Mail. A protocol for exchanging digitally signed and/or encrypted mail. that never gained much use. RFC 1421
p7c, p7m, p7s, p10 File types for S/MIME messages when saved to disk. RFC 2633
PGP Pretty Good Privacy. A protocol for exchanging digitally signed and/or encrypted mail. IMC's discussion of S/MIME and OpenPGP
PKI Public Key Infrastructure. The mechanisms used both to allow a recipient of a signed message to trust the signature and to allow a sender to find the encryption key for a recipient.
PKIX Internet X.509 Public Key Infrastructure. The name of the IETF working group creating standards for PKI on the Internet. http://www.imc.org/ietf-pkix/
POP, POP3 Post Office Protocol. A method for mail clients to retrieve mail from a message store. POP is more widely used than the IMAP protocol, which has more features. RFC 1939
public key cryptography A method for creating two keys (also called a key pair) that can be used to encrypt and decrypt messages. One of the two keys, the public key, is widely published, while the other key, the private key is kept secret. When you want to encrypt a message for a recipient, you use that recipient's public key; only someone with the private key can decrypt the message. When you want to digitally sign a message, you use your private key; anyone with your public key can then check the signature and verify that only you could have signed the message.
RFC Request For Comments. The primary mechanism used by the IETF to publish documents, including standards. IMC's list of mail standards and drafts
RFC 822 The specification for the format of Internet mail messages. This term is mostly used to describe the message headers. RFC 822
RSA Rivest-Shamir-Adelman. The name of a cryptographic key-exchange algorithm popular in many security protocols. Also the name of the company which controls the US patent on the algorithm. RFC 2313
S/MIME Secure MIME. A protocol for exchanging digitally signed and/or encrypted mail. IMC's discussion of S/MIME and OpenPGP
SASL Simple Authentication and Security Layer. A standard method for authentication that is used in many applications protocols. RFC 2222
server, mail There are many definitions for "mail server". It can be a host computer that uses the SMTP protocol, or simply software that uses the SMTP protocol. In some cases, it refers to a host system that holds a message store.
SMTP Simple Mail Transport Protocol. The standard for servers that move mail over the Internet. RFC 821
spam Slang for unsolicited bulk email (UBE). IMC's discussion of UBE
SSL Secure Sockets Layer. A protocol for encryption and authentication of Internet connections. See TLS.
TLS Transport Layer Security. The standardized version of SSL. RFC 2246
Triple DES A cryptographic algorithm for repeated DES operations that have the effect of increasing the security of the encrypted message. American National Standards Institute, ANSI X9.52-1998, "Triple Data Encryption Algorithm Modes of Operation"
UBE Unsolicited bulk email (also called spam). IMC's discussion of UBE
Unicode An encoding of the scripts of essentially all of the world's human languages. http://www.unicode.org/
URI Uniform Resource Identifier. See URL.
URL Uniform Resource Locator. A method for specifying the location of a resource on the Internet. RFC 1738
URN Uniform Resource Name. URNs serve as persistent, location-independent, resource identifiers. RFC 2141
vCalendar A format for calendaring and scheduling information. The vCalendar specification was created by the Versit consortium and is now managed by IMC. IMC's discussion of vCard and vCalendar
vCard A format for personal information such as would appear on a business card. The vCard specification was created by the Versit consortium and is now managed by IMC. IMC's discussion of vCard and vCalendar
vcf File type for vCards when saved to disk.
WG Working Group. Usually used with reference to the IETF.
X.400 Specification for mail clients and servers. CCITT Recommendations X.400-X.430: Message Handling Systems
X.500 Specification for global directory servers and access. ITU-T Recommendation X.500 (1997), ISO/IEC 9594-1:1997, Information technology - Open Systems Interconnection - The Directory: Overview of concepts, models and services
X.509 Specification of the format of digital certificates. See also PKIX. ITU-T Recommendation X.509 (1997), ISO/IEC 9594-8:1997, Information technology - Open Systems Interconnection - The Directory: Authentication framework.
X9.42 A specification for methods of using the Diffie-Hellman algorithms. American National Standards Institute, "Agreement Of Symmetric Keys Using Diffie-Hellman and MQV Algorithms", ANSI draft, 1998.

Term	Definition	Reference
ASN.1	Abstract Syntax Notation (1). A method for describing data that is used in many other standards.	CCITT, Recommendation X.208, "Specification of Abstract Syntax Notation One (ASN.1)"
CAST	A cryptographic encryption algorithm that is an optional part of some standards.	RFC 2144
clear-signed message	A digitally signed S/MIME or PGP message in which the content of the message is readable even if the signature is not.	RFC 1847
client, mail	A program for viewing mail. Mail clients usually also retrieve mail from message stores using either the POP or IMAP protocols, although some mail clients read mail directly from disk. Mail clients are usually controlled by people, but some mail client programs are automated processes.
CMS	Cryptographic Message Syntax. The internal format of an S/MIME message.	RFC 2630
cryptography	The study and practice of keeping data secure. Two common applications of cryptography are privacy (preventing unauthorized viewing of data) and authentication (proving one's identity to access data or as the source of a message).	Cryptography links kept at Counterpane Systems
DES	Data Encryption Standard. A cryptographic encryption algorithm that is part of many standards.	American National Standards Institute, ANSI X3.106, "American National Standard for Information Systems - Data Link Encryption"
Diffie-Hellman	A cryptographic key-exchange algorithm that is part of many standards. See also X9.42.
digital signature	A method for proving that the holder of a private key is the originator of a message
DSS	Digital Signature Standard. A cryptographic signature algorithm that is part of many standards. Also called DSA (Digital Signature Algorithm).	National Institute of Standards and Technology, FIPS Pub 186: Digital Signature Standard.
ESMTP	Extended Simple Mail Transfer Protocol. An extension to SMTP that gives a framework for additional extensions.	RFC 1869
ETRN	An ESMTP service extension for starting a remote message queue, such as for mail servers that are normally not connected to the Internet.	RFC 1985
FAQ	Frequently Asked Question. Usually, this is a document that lists frequently asked questions on a particular topic and gives answers to the questions.
i18n	Abbreviation for "internationalization".	IMC's mail internationalization information
IAB	Internet Architecture Board. The body that helps define the overall architecture and design of Internet protocols. The IAB is the technical advisory group of the ISOC.	http://www.iab.org/iab/
iCalendar	A format for calendaring and scheduling information. The term iCalendar generally refers to the protocols associated with the iCalendar format, such as the methods to exchange iCalendar objects.	http://www.imc.org/ietf-calendar/
IESG	Internet Engineering Steering Group. The group who oversees the IETF working group process and determines which proposals become standards.	http://www.ietf.org/iesg.html
IETF	Internet Engineering Task Force. The main organization that creates protocol standards for the Internet.	http://www.ietf.org/
IMAP, IMAP4	Internet Message Access Protocol. A method for mail clients to retrieve mail from a message store. IMAP is newer and has more features than the more popular POP protocol.	RFC 2060
Internet Draft	A document that is offered for review to the IETF.	IMC's list of mail standards and drafts
IMC	Internet Mail Consortium. The trade group for the Internet mail industry.	http://www.imc.org/
ISOC	Internet Society. The longest-standing organization promoting the use of the Internet.	http://www.isoc.org/
LDAP	Lightweight Directory Access Protocol. A simpler protocol for directory access than X.500.	RFC 2251
mailing list	A system for distributing messages to many people at once. A simple mailing list is a set of names that a single message is distributed to. A typical mailing list processor is a program that allows people to subscribe and unsubscribe from a list as well as managing the sending of messages to the lists' subscribers.
MAPI	Messaging Applications Programming Interface. A proprietary interface to client mail servers.
message store	The location where messages that are received by an SMTP server are held, waiting for mail clients to retrieve them. Message stores are usually just files on a hard disk, although some are databases.
MHTML	MIME-enhanced HTML. A method for sending aggregated HTML documents (such as ones with images) in a single MIME message.	RFC 2110
MIME	Multipurpose Internet Mail Extensions. A structured format for messages which allows a single message to contain many parts.	RFC 2045
MOSS	MIME Object Security Services. A protocol for exchanging digitally signed and/or encrypted mail. that never gained much use.	RFC 1848
MTA	Mail Transfer Agent. A server running the SMTP protocol.
MUA	Mail User Agent. See client, mail.
multipart	A type of MIME message that contains more than one part.	RFC 2046
OpenPGP	A newer version of PGP that was created in the IETF.	RFC 2440 and IMC's discussion of S/MIME and OpenPGP
PEM	Privacy Enhanced Mail. A protocol for exchanging digitally signed and/or encrypted mail. that never gained much use.	RFC 1421
p7c, p7m, p7s, p10	File types for S/MIME messages when saved to disk.	RFC 2633
PGP	Pretty Good Privacy. A protocol for exchanging digitally signed and/or encrypted mail.	IMC's discussion of S/MIME and OpenPGP
PKI	Public Key Infrastructure. The mechanisms used both to allow a recipient of a signed message to trust the signature and to allow a sender to find the encryption key for a recipient.
PKIX	Internet X.509 Public Key Infrastructure. The name of the IETF working group creating standards for PKI on the Internet.	http://www.imc.org/ietf-pkix/
POP, POP3	Post Office Protocol. A method for mail clients to retrieve mail from a message store. POP is more widely used than the IMAP protocol, which has more features.	RFC 1939
public key cryptography	A method for creating two keys (also called a key pair) that can be used to encrypt and decrypt messages. One of the two keys, the public key, is widely published, while the other key, the private key is kept secret. When you want to encrypt a message for a recipient, you use that recipient's public key; only someone with the private key can decrypt the message. When you want to digitally sign a message, you use your private key; anyone with your public key can then check the signature and verify that only you could have signed the message.
RFC	Request For Comments. The primary mechanism used by the IETF to publish documents, including standards.	IMC's list of mail standards and drafts
RFC 822	The specification for the format of Internet mail messages. This term is mostly used to describe the message headers.	RFC 822
RSA	Rivest-Shamir-Adelman. The name of a cryptographic key-exchange algorithm popular in many security protocols. Also the name of the company which controls the US patent on the algorithm.	RFC 2313
S/MIME	Secure MIME. A protocol for exchanging digitally signed and/or encrypted mail.	IMC's discussion of S/MIME and OpenPGP
SASL	Simple Authentication and Security Layer. A standard method for authentication that is used in many applications protocols.	RFC 2222
server, mail	There are many definitions for "mail server". It can be a host computer that uses the SMTP protocol, or simply software that uses the SMTP protocol. In some cases, it refers to a host system that holds a message store.
SMTP	Simple Mail Transport Protocol. The standard for servers that move mail over the Internet.	RFC 821
spam	Slang for unsolicited bulk email (UBE).	IMC's discussion of UBE
SSL	Secure Sockets Layer. A protocol for encryption and authentication of Internet connections. See TLS.
TLS	Transport Layer Security. The standardized version of SSL.	RFC 2246
Triple DES	A cryptographic algorithm for repeated DES operations that have the effect of increasing the security of the encrypted message.	American National Standards Institute, ANSI X9.52-1998, "Triple Data Encryption Algorithm Modes of Operation"
UBE	Unsolicited bulk email (also called spam).	IMC's discussion of UBE
Unicode	An encoding of the scripts of essentially all of the world's human languages.	http://www.unicode.org/
URI	Uniform Resource Identifier. See URL.
URL	Uniform Resource Locator. A method for specifying the location of a resource on the Internet.	RFC 1738
URN	Uniform Resource Name. URNs serve as persistent, location-independent, resource identifiers.	RFC 2141
vCalendar	A format for calendaring and scheduling information. The vCalendar specification was created by the Versit consortium and is now managed by IMC.	IMC's discussion of vCard and vCalendar
vCard	A format for personal information such as would appear on a business card. The vCard specification was created by the Versit consortium and is now managed by IMC.	IMC's discussion of vCard and vCalendar
vcf	File type for vCards when saved to disk.
WG	Working Group. Usually used with reference to the IETF.
X.400	Specification for mail clients and servers.	CCITT Recommendations X.400-X.430: Message Handling Systems
X.500	Specification for global directory servers and access.	ITU-T Recommendation X.500 (1997), ISO/IEC 9594-1:1997, Information technology - Open Systems Interconnection - The Directory: Overview of concepts, models and services
X.509	Specification of the format of digital certificates. See also PKIX.	ITU-T Recommendation X.509 (1997), ISO/IEC 9594-8:1997, Information technology - Open Systems Interconnection - The Directory: Authentication framework.
X9.42	A specification for methods of using the Diffie-Hellman algorithms.	American National Standards Institute, "Agreement Of Symmetric Keys Using Diffie-Hellman and MQV Algorithms", ANSI draft, 1998.