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Common Terms

Common Terms used for Email Services


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.

Acceptance Rate - The percentage of email messages a mail server will accept. Don’t assume that emails go to the inbox once it’s accepted by the email server.

Affiliate - A marketing partner that promotes your products or services under a payment-on-results agreement.

Affirmative Consent - An active request by a reader or subscriber to receive advertising or promotional information, newsletters, etc. 

Alert - Email message that notifies subscribers of an event or special price.

Allow List - A list of trusted IP addresses and domains for which all mail is delivered, bypassing spam filters.

API - (Application Program Interface) How a program (application) accesses another to transmit data. A client may have an API connection to load database information to an email vendor automatically and receive data back from the email.

ASP - (Application Service Provider) Company that provides a Web-based service. Clients don’t have to install software on their own computers; all tasks are performed on (hosted on) the ASP’s servers.

Attachment - An attachment is a file that is sent along with an email message.  It may be an image, a document, or an mp3 file, for example.

Authentication - A term that refers to standards (SPF, 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.

Autoresponder - Automated email message-sending capability, such as a welcome message sent to all new subscribers when they join a list.  It may be triggered by joins, unsubscribes, all email sent to a particular mailbox. 


BCC - (Blind Carbon Copy) A copy of an email message sent to a recipient whose email address does not appear in the message. There is typically a field to enter this option under the field for the primary email address.

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.

Backscatter - Backscatter is a delivery failure report generated by a junk email that used an innocent third party's email address as the sender (which address receives the delivery failure message).

Base64 - Base64 is a method for encoding arbitrary binary data as ASCII text, to be used, for example, in an email body.

Blacklist / Blocklist - 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. 

Bounce - A message that is returned to the server that sent it. Bounced emails are classified as either “hard” or “soft” bounces. A hard bounce indicates a permanent failure due to a non-existent address or a blocking condition by the receiver. A soft bounce means there has been a temporary failure due to a full mailbox or unavailable server.

Bounce Rate - Number of hard/soft bounces divided by the number of emails sent. This is an inexact number because some systems do not report back to the sender clearly or accurately.

Below the Fold - The bottom part of an email message that is only visible to the recipient when they scroll down the message. The term originally comes from print and refers to the bottom half of a folded newspaper.

Bulk Mail - When the same content goes out to a large group of people. Large scale email marketing.


Call to Action - The link or body copy that tells the recipient what action to take.

CAN-SPAM - (Controlling the Assault of Non-Solicited Pornography and Marketing Act of 2003) - This is the law outlining rules for commercial email and commercial messages. It established that email recipients have the right to make you stop emailing them (with violations for those who do not stop emails).

CAPTCHA - (Completely Automated Public Turing Test to Tell Computers and Humans Apart) This can be found on online forms, used to verify that a human not a computer is behind the form submission.

CC - (Carbon Copy) A copy of an email message sent to a recipient whose email address appears in the message's CC header field.

Commercial Email - Email whose purpose, as a whole or in part, is to sell or advertise a product or service or if its purpose is to persuade users to perform an act, such as to purchase a product or click to a Web site whose contents are designed to sell, advertise, or promote.

Complaint Rate - A percentage of how many subscribers marked an email message as spam.

Contact List - Another term for your subscriber list or mailing list.

Content - All the material in an email message except for the codes showing the delivery route and return-path information. Includes all words, images, and links.

Creative - An email message's copy and any graphics.

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

CSS - (Cascading Style Sheets) A markup language used to design emails and web pages. 


Dedicated IP - Refers to an IP address from which only you may send email.

Deliverability - The art and science of getting emails from a sender all the way to subscribers’ inboxes.

Deny list - A list of IP addresses that are known to send unsolicited and/or unwanted emails. ISPs and enterprises use deny lists to identify and filter illegitimate mail streams.

Deploy - The act of sending the email campaign after testing.

DKIM - (DomainKeys Identified Mail) An email authentication technique that links a domain name to an email message. Used to verify an email's authenticity and to increase deliverability rates.

DMARC - (Domain-based Message Authentication, Reporting, and Conformance) An email protocol that when published for a domain, controls what happens if a message fails authentication tests (i.e., the recipient server can't verify that the message's sender is who they say they are).

DNS - (Domain Name Server or Domain Name System) An Internet service that translates domain names into IP addresses.

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 SocketLabs.com). 

Domain Name System - DNS translates a domain name into an IP address to find the owner’s site.

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

Drip Campaign - A set of emails sent out in sequence to the same list of contacts.

Drip Marketing - Usually refers to automated marketing that sends a series of messages to prospects over time. Autoresponders are a type of drip marketing.


Email address - The combination of a unique username and a sender domain (JohnDoe@anywhere.com). The email address requires both the username and the domain name.

Email Body - The email body is the main part of an email message that contains the message’s text, images, and other data (such as attached files).

Email Campaign - A series of emails designed to accomplish a marketing goal.

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

Email Domain - The domain name, website, or URL that an email is sent from. Typically, this is your company’s primary domain name.

Email filter - A software tool that categorizes, sorts, or blocks incoming email, based either on the sender, the email header or message content. Filters may be applied at the recipient's level, at the email client, the ISP, or a combination.

Email Friendly Name (Display Name, from name) - The portion of the email address that is displayed in most, though not all, email readers in place of, or in addition to, the email address.

Email headers - The section of an email message that contains the sender's and recipient's email addresses as well as the routing information. It is located at the top of the original email sent to a recipient. I will show everywhere the email has been.

Email List - This is a permission-based email list that you build yourself with opt-in subscribers. One of your marketing team’s most valuable lists.

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

Email Phishing - A fraudulent email sent from a spammer that says something has gone wrong with a critical account and asks the recipient to give their bank account login information or other sensitive information via a link in the email. The spammer then collects the information the unknowing email recipient has given them.

Email Prefix - The portion of the email address to the left of the @ sign.

Email Queue - The email messages that are all set up and ready to go but are waiting for your email service provider to deploy them.

Engagement - An umbrella term that covers every possible interaction an email subscriber can have with your message, like opens, clicks, shares and more.

ESP - (Email Service Provider) The company that provides software and hardware to manage your list and deploy and track your email messages.

Exchange Server - Exchange is an email based collaborative communications server for businesses. It provides a collaboration environment for secure messaging inside and outside a business or an organization. It also supports group scheduling capabilities, discussion groups, team folders, mobile and web access, and a host of other features. It provides a robust syncing tool for all your email, calendar, contacts, and other communications between your desktop, mobile device, and Internet connection. With your Hosted Exchange Email account and your Exchange ActiveSync-enabled phone, you have secure access to communications from anywhere. Often used by businesses to run various applications like mail, calendars, and address books that use IMAP style syncing. You will probably be using this for your work email, if you work for a medium to large company or own your own business.


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

Feedback Loop - The process by which an ISP forwards emails reported as spam (see complaint) for immediate removal by the sender. For a deeper dive into feedback loops check out this blog post.

Filters - Filters automatically move incoming emails into separate folders according to criteria that you specify. These criteria may be based on who the email is from, the priority, the subject, the main message, etc. This is a useful feature if you have a lot of incoming emails that need some way of being automatically organized.

Firewall - A program or set of programs designed to keep unauthorized users or messages from accessing a private network. The firewall usually has rules or protocols that authorize or prohibit outside users or messages. In email, a firewall can be designed so that messages from domains or users listed as suspect because of spamming, hacking, or forging will not be delivered.

Footer - This is a short block of text at the end of an email message. It identifies the sender, may provide a bit more of additional information (company name, mail address, contact information) and fulfills CAN SPAM regulations.

Forwards - A count of how many times one of your subscribers forwarded a message you sent them to someone else.

From - Whatever appears in the email recipient's inbox as your visible "from" name. Chosen by the sender. May be a personal name, a brand name, an email address, a blank space, or alpha-numeric gobbledygook. Note - this is not the actual "from" contained in the header (see below) and may be different than the email reply address. Easy to fake. Aka Email Friendly Name.

From - The From-header field, in an email, contains the message's author. It must list the email address, and one can add a name as well.

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.

Full-service provider - An email vendor that also provides strategic consulting and creative support, in addition to sending messages.


GB - A GB (gigabyte) is made up of 1000 MB (megabytes) or 10? (1 billion) bytes. A byte is a basic unit of storing information electronically made up of 8 bits; each bit has two states (on or off).


Hard Bounce - This is the failed delivery of an email due to the destination address being non-existent, invalid, or blocked.

Header - Routing and program data at the start of an email message, including the sender's name and email address, originating email server IP address, recipient IP address and any transfers in the process.

Host name - The name of a computer on the Internet (such as www.lsoft.com).

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

HTML message - Email message which contains any type of formatting other than text. This may be as simple as programming that sets the text in a specific font (bold, italics, Courier 10 point, etc.). It also includes any graphic images, logos, and colors.

Hurricane MTA - The SocketLabs On-Premises product.

Hygiene - The process of cleaning a database to correct incorrect or outdated values. See also List Hygiene.


IMAP - Internet Message Access Protocol, a standard protocol for accessing email from a server.

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 - A unique number assigned to each device connected to the Internet. An IP address can be dynamic, meaning it changes each time an email message is deployed, or it can be static meaning it does not change. A static IP address is recommended for senders of commercial email.

IP Warmup - Slowly sending out an increasing number of emails from an IP address to build a positive reputation for the 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. 


Jpeg or jpg - (Joint Photographic Experts Group) A common file format of images.


LAN - (Local Area Network) A computer network, although geographically limited, usually to the same building, office, etc.

Landing Page - Where a subscriber will go after they click on a link in your emails. Can also apply to where someone goes after they click on an advertisement, or any other content format online.

List - The list of email addresses to which you send your message. Can be either your house list or a third-party list that sends your message on your behalf.

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 Hygiene - How well your list’s information is kept up to date. This includes removing unsubscribes and inactive addresses.

List management - How a mailing list is set up, administered, and maintained. The list manager has daily responsibility over list operation, including processing subscribes and unsubscribes, bounce management, list hygiene, etc. The list manager can be the same as the database manager but is not always the same person as the list owner. See list owner.

List owner - The organization or individual who has gathered a list of email addresses. Ownership does not necessarily imply "with permission."

List Segmentation - This is a target audience or group of individual email addresses for which your email message is relevant. Because of this targeting / segmentation, you can expect to get a higher response rate and fewer unsubscribes and spam reports.

Local host - The computer to which a user's terminal is directly connected, and which the email comes from.


Mailing list - A list of email addresses that receive mailings or discussion-group messages.

Mailto - An HTML tag that allows visitors on a site to click on a link that creates a new message in their default email program. It is possible to set not only a default email recipient but also default subject and message body content.

MTA - (Mail Transfer Agent) Software that transfers electronic mail messages from one computer to another using a client–server application architecture. An MTA implements both the client (sending) and server (receiving) portions of the SMTP (Simple Mail Transfer Protocol).

MX Record - A Mail Exchanger (MX) record in the DNS system specifies a mail server responsible for accepting email addresses on behalf of a domain. The MX records associated with a domain assure that the email is properly routed via Simple Mail Transfer Protocol (SMTP).


Onboarding - A marketing technique of educating new customers or clients in your business’s strengths and features. Welcome emails are common examples of onboarding.

Open Relay - An SMTP server configured in such a way that it allows anyone on the Internet to send email through it, not just mail destined for or originating from known users. This is not a recommended configuration because it can be exploited by spammers – and servers with open relays are routinely blocked and/or deny listed.

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. 


Permission - The implicit approval given when a person actively requests to have their own email address added to a list.

Phishing - Technique for acquiring information such as usernames, passwords, credit cards, social security numbers and other personal data by masquerading as a trusted business like a bank or credit card company. With phish messages, the email appears to be sent by the trusted entity and the consumer is tricked into providing their personal information.

Physical Address - This is the physical, street address of the company sending the email. Its inclusion (in the footer most often) is a legal mandate for all email marketing messages.

Plain text - Text in an email message that contains no formatting elements (i.e.  color, bold, italics, etc.), pictures, or HTML.

.png - (Portable Network Graphics) A file format commonly used online and in email messages.

Pre-Header Text - Part of an email message that is always text and appears right below the subject line when viewed in an inbox.

Privacy Policy - Every website is required to have a privacy policy. A privacy policy explains to website visitors and to email subscribers how their information is collected and used.

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

Proxy - A computer system or router that breaks the connection between sender and receiver, giving anonymity.

Public Key Cryptography - Public key cryptography uses a key with two parts. The public key part is used for encryption exclusively for the recipient, whose private key part is applied for decryption. For public key cryptography to be safe it is important that only the intended recipient knows the private part of the key.


Queue - Where an email message goes after you send it but before it gets delivered to its destination. 


Read email - Not measurable. Only opens and clicks are measurable in any way. You can never know if a recipient simply read your message.

Registration - The process where someone not only opts into your email program but provides some additional information, such as name, address, demographic data, or other relevant information, usually by using a Web form.

Reply-to - The email address that receives messages sent from users who click “reply” in their email clients. Can differ from the “from” address which can be an automated or unmonitored email address used only to send messages to a distribution list. “Reply-to” should always be a monitored address.

Reverse DNS Lookup - The process of looking up and translating an IP address into a domain name.


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

Scraping - A spamming technique. Scraping is when scraping software goes out on the Internet to find any email address it can. Therefore, many email addresses on contact forms use formatting like “Barbara (at) yahoo dot com”. The site owner hopes the spelled-out email address will confuse scraper bots.

Segment - The ability to slice a list into specific pieces determined by various attributes, such as open history or name source.

Segmentation - The email marketing technique of breaking a list up into different segments. You can segment a list dozens of different ways, including by subject preferences, last opened date and more.

SenderID - An email authentication standard developed by Microsoft that compares the email sender’s “From” address to the IP address to verify that it is authorized to send email from that domain.

Sent emails - Number of email names transmitted in a single broadcast. Does not reflect how many were delivered or viewed by recipients.

Server - A program or computer system that stores and distributes email from one mailbox to another, or relays email from one server to another in a network.

Shared IP Address - In the context of deploying email, this means that a single IP address or IP range is used to send email for multiple domains. The reputation of this IP is based on the aggregate performance of all the senders that use it.

Shared server - An email server used by more than one company or sender.  Senders sharing a server risk having emails blocked by major ISPs if one of the other users does something to get the server's IP address blacklisted. See dedicated server.

Single Opt In - When users sign up for email list, but don’t need to confirm their email address with the email service provider. The downside is that someone can sign up email recipients without their permission. 

SMPT - (Simple Mail Transfer Protocol) The protocol used for sending email over the internet, a set of commands that authenticates and directs the transfer of mail.

Soft Bounce - This is the failed delivery of an email due to a temporary issue (full mailbox or an unavailable server).

Spam - Unwanted, unsolicited junk email sent to many recipients.

Spam Filter - Software filters that block email on a range of attributes from words or phrases within the email to header information and other factors. The goal is to identify spam before it is delivered to the inbox. For more on how to stay out of the spam folder, read our free Tips and Tricks Guide.

Spam Trap - An email address used by anti-spam entities to trap spammers.

Spammer - Anyone who sends unwanted emails.

SPF - (Sender Policy Framework) An email authentication standard that compares the email sender’s actual IP address to a list of IP addresses authorized to send mail from that domain. The IP list is published in the domain’s DNS record.

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.

Subject Line - An email message’s equivalent of a headline, or title that appears in the email client message list.

Subscribe - The process of joining a mailing list, either through an email command, by filling out a Web form, or offline by filling out a form or requesting to be added verbally.

Subscriber - The people who have signed up to receive your email messages.

Suppression List - A list of email addresses kept by an organization that cannot be mailed because the recipients have request removal either by unsubscribing or by logging a complaint.


Text newsletter - Plain newsletter with words only, no colors, graphics, fonts, or pictures; can be received by anyone who has email.

Thank You Page - The page new subscribers see after they’ve entered their email address into the opt-in form and clicked the subscribe button.

Throttling - Sending email messages out in batches or at a slower rate instead of all at once. This improves deliverability rates and server load management.

To - The To line of an email contains its primary recipient or recipients. All recipients in the To line is visible to all other recipients, possibly by default.

Transactional Emails - Emails sent to confirm orders, reservations, password resets, and anything else. They have higher engagement rates than promotional emails.


VERP - (Variable Envelope Return Path) A technique used to enable automatic detection and removal of undeliverable e-mail addresses. It works by using a different return path (also called "envelope sender") for each recipient of a message.


Unique Clicks - This is how many individual subscribers have clicked on links in your emails. It is more specific than overall click-through rate, which just shows how many times your emails were clicked.

Unique Opens - Some subscribers will open an email more than once. Unique opens show how many individuals have opened your emails, not just how many times your emails were opened.

Unsubscribe - To remove oneself from an email list, either via an emailed command to the list server or by filling in a Web form.

URL - (Uniform Resource Locator) The address of a file or Web page accessible on the Internet (for example, https://www.socketlabs.com

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


Welcome message - Message sent automatically to new list members as soon as their email addresses are added successfully.

Whitelist / Safelist - Advance-authorized list of email addresses, held by an ISP, subscriber, or other email service provider, which allows email messages to be delivered regardless of spam filters.

WHOIS Record - A record of domain registration whereby you can discover when and by whom a domain was registered along with contact information and expiry dates.


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.