Glossary of Email Terms

Glossary of Email Terms

Find definitions to common email list management, email marketing and other industry terminology.

Table of Contents:



Above the fold: The top part of an email message that is visible to the recipient without the need for scrolling. The term originally comes from print and refers to the top half of a folded newspaper.

Alias: A unique and usually shorter URL (link) that can be distinguished from other links even if they ultimately go to the same Web page. This makes it possible to track which message led viewers to click on the link.

ASP: Application Service Provider – A company that offers organizations access over the Internet to applications and related services that would otherwise have to be located on site at the organization's premises.

Attachment: An audio, video or other data file that is attached to an email message.

Autoresponder: A computer program that automatically responds with a prewritten message to anyone who sends an email message to a particular email address or uses an online feedback form.

Authentication: A term that refers to standards, such as Sender ID, SPF and DomainKeys/DKIM, that serve to identify that an email is really sent from the domain name and individual listed as the sender. Authentication standards are used to fight spam and spoofing.


B2B: Business-to-Business – The exchange of information, products or services between two businesses – as opposed to between a business and a consumer (B2C).

B2C: Business-to-Consumer – The exchange of information, products or services between a business and a consumer – as opposed to between two businesses (B2B).

Back-end: (1) The part of the computer that changes source code into object code (machine read code). (2) The part of the program that runs on a server in a client/server application.

Bayesian filter: A spam filter that evaluates email message content to determine the probability that it is spam. Bayesian filters are adaptable and can learn to identify new patterns of spam by analyzing incoming email.

BITNET: Abbreviation for "Because It's Time NETwork." BITNET is primarily a network of sites for educational purpose and is separate from the Internet. Email is exchanged at no charge between BITNET and the Internet.

Blacklist: A list containing email addresses or IP addresses of suspected spammers. Blacklists are sometimes used to reject incoming mail at the server level before the email reaches the recipient.

Block: An action by an Internet Service Provider to prevent email messages from being forwarded to the end recipient.

Bounces: Email messages that fail to reach their intended destination. "Hard" bounces are caused by invalid email addresses, whereas "soft" bounces are due to temporary conditions, such as overloaded inboxes.


CGI: Common Gateway Interface – A specification for transferring information between a Web server and a CGI program. CGI programs are often used for processing email subscriptions and Web forms.

Challenge-Response: An authentication method that requires a human to respond to an email challenge message before the original email that triggered the challenge is delivered to the recipient. This method is sometimes used to cut down on spam since it requires an action by a human sender.

Click-through tracking: The process of tracking how many recipients clicked on a particular link in an email message. This is commonly done to measure the success of email marketing campaigns.

Click-through rate: In an email marketing campaign, the percentage of recipients who clicked on a particular link within the email message.

Conditional blocks: A text fragment that is pasted into an email message only if certain conditions are met (for instance the recipient lives in a certain area). Conditional blocks allow email marketers to create more personalized mailings.

Conversion rate: A measure of success for an email marketing campaign (for instance the number of recipients who completed a purchase). With email marketing, conversion rates are relatively easy to calculate because of the technology's measurable nature.

CPM: Cost Per Thousand – An industry standard measure for ad impressions. Email has a relatively low CPM compared to other marketing channels (Note: "M" represents thousand in Roman numerology).

CRM: Customer Relationship Management – The methodologies, software, and Internet capabilities that help a company manage customer relationships in an efficient and organized manner.


Database Management System: A database system that provides possibilities for users to connect LISTSERV® to a database back-end and, hence, send out personalized messages to customers, according to their demographic information and preferences.

Deliverability: A term that refers to the best practices and authentication techniques of mass email communication that improve the likelihood that opt-in email messages are successfully delivered to end recipients instead of being erroneously blocked by ISPs and spam filters.

Discussion group: An email list community where members can obtain and share information. Every member can write to the list, and in doing so, everyone subscribed to the list will receive a copy of the message.

DNS: Domain Name Server (or system) – An Internet service that translates domain names into IP addresses.

DomainKeys/DKIM: DomainKeys/DomainKeys Identified Mail are cryptographic authentication solutions that add signatures to email messages, allowing recipient sites to verify that the message was sent by an authorized sender and was not altered in transit.

Domain name: A name that identifies one or more IP addresses. Domain names always have at least two parts that are separated by dots (for instance The part on the left is the second-level domain (more specific), while the part on the right is the top-level domain (more general).

Domain Throttling: A technique that allows you to limit the number of email messages sent to a domain within a certain time frame. It is used to comply with ISPs and to avoid tripping spam filters. Many ISPs have their own policies and preferred limits.

Double opt-in: The recommended procedure for subscribing email recipients to an email list or newsletter. Once a person requests to subscribe to a list, a confirmation email message is automatically sent to the supplied email address asking the person to verify that they have in fact requested to be included in future mailings.

Download: To transfer a copy of a file from an Internet server to one's own computer.


Email: Email allows you to send and receive text, HTML, images and other data files over the Internet. Email is one of the most popular online activities and has become a vital tool for electronic commerce.

Email bounces: Email messages that fail to reach their intended destination. "Hard" bounces are caused by invalid email addresses, whereas "soft" bounces are due to temporary conditions, such as overloaded inboxes.

Email client: The software that recipients use to read email. Some email clients have better support for HTML email than others.

Email harvesting: The disreputable and often illegal practice of using an automated program to scan Web pages and collect email addresses for use by spammers.

Email header: The section of an email message that contains the sender's and recipient's email addresses as well as the routing information.

Email marketing: The use of email (or email lists) to plan and deliver permission-based marketing campaigns.


False positive: A legitimate email message that is mistakenly rejected or filtered by a spam filter.

Forward DNS Lookup: A Forward DNS Lookup, or just DNS Lookup, is the process of looking up and translating a domain name into its corresponding IP address. This can be compared to a Reverse DNS Lookup, which is the process of looking up and translating an IP address into a domain name.

FQDN: Fully Qualified Domain Name – A name consisting of both a host and a domain name. For example, is a fully qualified domain name. www is the host; lsoft is the second-level domain; and .com is the top-level domain.

Freeware: A free computer program usually made available on the Internet or through user groups.

FTP: File Transfer Protocol – Used for uploading or downloading files to and from remote computer systems on a network using TCP/IP, such as the Internet.


Gateway: This is a hardware or software set-up that functions as a translator between two dissimilar protocols. A gateway can also be the term to describe any mechanism providing access to another system (e.g AOL might be called a gateway to the Internet).


Hard bounces: Email messages that cannot be delivered to the recipient because of a permanent error, such as an invalid or non-existing email address.

Host: When a server acts as a host it means that other computers on the network do not have to download the software that this server carries. For instance, L-Soft offers the EASESM and ListPlex® products, which customers can use without having to store the software on their own computers.

Host name: The name of a computer on the Internet (such as

HTML: HyperText Markup Language – The most commonly used coding language for creating Web pages. HTML can also be used in email messages.


IMAP: Internet Message Access Protocol – A protocol used to retrieve email messages. Most email clients use either the IMAP or the POP protocol.

In-house list: A list of email addresses that a company has gathered through previous customer contacts, Web sign-ups or other permission-based methods. In-house lists typically generate higher conversion rates than rented lists.

Internet: The largest worldwide computer network.

Intranet: Contrary to the public Internet, an intranet is a private network inside a company or organization.

IP address: An IP (Internet Protocol) address is a unique identifier for a computer on the Internet. It is written as four numbers separated by periods. Each number can range from 0 to 255. Before connecting to a computer over the Internet, a Domain Name Server translates the domain name into its corresponding IP address.

ISP: Internet Service Provider – A company that provides access to the Internet, including the World Wide Web and email, typically for a monthly fee.


LAN: Local Area Network, which is a computer network, although geographically limited, usually to the same building, office, etc.

List broker: A company that sells or rents lists of email addresses. Some list brokers are not reputable and sell lists with unusable or unsubstantiated candidates. It is therefore advisable for email marketers to build their own internal lists.

List owner: The owner of an email list defines the list's charter and policy (i.e. what the list is about and what are the general rules that all subscribers must accept in order to be subscribed to the list). The list owner is also responsible for administrative matters and for answering questions from the list subscribers.

LISTSERV®: L-Soft's email list management software and the first automated mailing list program created. LISTSERV allows users to create opt-in email lists, such as email newsletters, announcement lists and discussion groups.

LISTSERV® Maestro: L-Soft's email marketing software that allows users to manage and track sophisticated, database-driven opt-in email marketing campaigns.


Mail-merge: A process that enables the delivery of personalized messages to large numbers of recipients. This is usually achieved using email list management software working in conjunction with a database.

Mainframe: A high-level computer often shared by multiple users connected by individual terminals.

Merge-purge: The act of removing duplicate email addresses from a coalesced list that is composed of two or more existing lists.

MIME: Multi-Purpose Internet Mail Extensions – An extension of the original Internet email standard that allows users to exchange text, audio or visual files.

Moderated list: Moderators must approve any message posted to an email list before it is delivered to all subscribers. It is also possible for the moderator to edit or delete messages. A moderated list thus puts the list owner in the equivalent position as an editor of a newspaper.

Multi-threading: A process though which a mail server can perform multiple concurrent deliveries to different domains, which greatly speeds up the delivery of large volumes of email.

Multipart/alternative: A message format that includes both text and HTML versions. Recipients can then open the message in their preferred format.


ODBC: Open DataBase Connectivity – A Microsoft standard for accessing different database systems from Windows, for instance Oracle or SQL.

Offload: To assume part of the processing demand from another device.

Open-relay: Open-relay is the third-party relaying of email messages though a mail server. Spammers looking to obscure or hide the source of large volume mailings often use mail servers with open-relay vulnerabilities to deliver their email messages.

Open-up tracking: The process of tracking how many recipients opened their email messages as part of an email marketing campaign. Open-up tracking is only possible using HTML mail.

Open-up rate: The percentage of recipients who opened their email messages. The open-up rate is often used to measure the success of an email marketing campaign.

Operating system: A program that manages all other programs in a computer, such as Windows or Unix.

Opt-in: An approach to email lists in which subscribers must explicitly request to be included in an email campaign or newsletter.

Opt-out: An approach to email lists in which subscribers are included in email campaigns or newsletters until they specifically request not to be subscribed any longer. This method is not recommended and may in some cases be illegal.

Out-of-office replies: Automatic email reply messages triggered by incoming email to a user's inbox, typically activated when users are on vacation or otherwise unavailable through email for an extended period.

Outsourcing: An arrangement where one company provides services to another company that would otherwise have been implemented in-house (See also "ASP").


Pass-along: An email message that gets forwarded by a subscriber to another person who is not subscribed to the list (See also "Viral Marketing").

Personalization: The insertion of personal greetings in email messages (for instance "Dear John" rather than the generic "Dear Customer"). Personalization requires email list management software that allows for so called mail-merge operations.

Plain text: Text in an email message that contains no formatting elements.

POP: Post Office Protocol – A protocol used to retrieve email from a mail server. Most email clients use either the POP or the newer IMAP protocol.

Privacy: A major concern of Internet users that largely involves the sharing of personally identifiable information, which includes name, birth date, Social Security number and financial data, for example.

Protocol: The set of formal rules that describe how to transmit data, especially across a network of computers.


Query: A subset of records in a database. Queries may be used to create highly specified demographics in order to maximize the effectiveness of an email marketing campaign.


Reverse DNS Lookup: A Reverse DNS Lookup is the process of looking up and translating an IP address into a domain name. This can be compared to a Forward DNS Lookup, which is the process of looking up and translating a domain name into its corresponding IP address.

Rich media: An Internet advertising term for a Web page that uses graphical technologies such as streaming video, audio files or other similar technology to create an interactive atmosphere with viewers.

Router (Routing System): The role of a route can be described as a bridge between two or more networks. The function of the router is to look at the destination addresses of the packets passing through it, and thereafter decide which route to send these packets on.


Scalability: The ability of a software program to continue to function smoothly as additional volume, or work is required of it.

Sender ID: Sender ID is an authentication protocol used to verify that the originating IP address is authorized to send email for the domain name declared in the visible "From" or "Sender" lines of the email message. Sender ID is used to prevent spoofing and to identify messages with visible domain names that have been forged.

Server: A program that acts as a central information source and provides services to programs in the same or other computers. The term can either refer to a particular piece of software, such as a WWW server, or to the machine on which the software is running.

Shareware: This term refers to software available on public networks.

Signature file: A short text file that email users can automatically append at the end of each message they send. Commonly, signature files list the user's name, phone number, company, company URL, etc.

SMTP: Simple Mail Transfer Protocol – A protocol used to send email on the Internet. SMTP is a set of rules regarding the interaction between a program sending email and a program receiving email.

Snail mail: Traditional or surface mail sent through postal services such as the USPS.

Sniffing: A method of determining whether email recipients are capable of receiving HTML-formatted messages. This procedure is not recommended as it is flawed and may result in inaccurate findings.

Soft bounces: Email messages that cannot be delivered to the recipient because of a temporary error, such as a full mailbox.

Spam: (Also known as unsolicited commercial email) – Unwanted, unsolicited junk email sent to a large number of recipients.

SPF: Sender Policy Framework – An authentication protocol used by recipient sites to verify that the originating IP address is authorized to send email for the domain name declared in the "MAIL FROM" line of the mail envelope. SPF is used to identify messages with forged "MAIL FROM" addresses.

Spoofing The disreputable and often illegal act of falsifying the sender email address to make it appear as if an email message came from somewhere else.

Streaming media: Audio and video files transmitted on the Internet in a continuous fashion.

Subject line: The part of an email message where senders can type what the email message is about. Subject lines are considered important by email marketers because they can often influence whether a recipient will open an email message.


Targeting: Using demographics and related information in a customer database to select the most appropriate recipients for a specific email campaign

TCP / IP: Transmission Control Protocol / Internet Protocol – This is the protocol that defines the Internet. TCP / IP was originally designed for the unix operating system, but is today available for every major kind of computer operating system.

Tracking: In an email marketing campaign, measuring behavioral activities such as click-throughs and open-ups.


URL: Uniform Resource Locator – The address of a file or Web page accessible on the Internet (for example,

User Interface: A set of controls such as buttons, commands and other devices that allow a user to operate a computer program.


Viral marketing: A marketing strategy that encourages email recipients to pass along messages to others in order to generate additional exposure.

Virtual hosting: A Web server hosting service that replaces a company's need to purchase and maintain its own Web server and connections to the Internet.

Virus: A program, macro or fragment of code that causes damage and can be quickly spread through Web sites or email.


Whitelist: A list of pre-authorized email addresses from which email messages can be delivered regardless of spam filters.

Worm: Malicious code that is often spread through an executable attachment in an email message.


XML: Extensible Markup Language – A flexible way to create standard information formats and share both the format and the data on the World Wide Web.

LISTSERV is a registered trademark licensed to L-Soft international, Inc.

See Guidelines for Proper Usage of the LISTSERV Trademark for more details.

All other trademarks, both marked and unmarked, are the property of their respective owners.