Email Deliverability Terms You Need to Know (part 2)

As with in any industry, those of us in the email deliverability world tend to throw out a lot of jargon. If you're new to the wonderful world of email, much of it may be jibberish to you. To help newbies and vertrans alike, I have put together a list of the top 80 email deliverability terms you should know. Below is part two of three (I-R). Part one (A-H) was published last week, and part three (S-Z) will be live next week.  

Inactives: Also referred to as "non-responders". Defined as the portion of your email recipient list who have not taken any action on your emails (opens, clicks) in a certain amount of time.

Inbox Placement Rate (IPR): The rate of emails that were delivered to the inbox, versus the junk folder.  Calculated as Number of Emails Delivered to the Inbox divided by Total Number of Emails Sent.

Infrastructure: Refers to the actual hardware used to deploy your emails or have your emails deployed on your behalf by an Email Service Provider (ESP). The hardware is commonly referred to as your Mailing Transport Agent (MTA).

Internet Service Provider (ISP): A company in the business of providing access to consumers and business to the internet.

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 or campaign goes out, or it can be static, meaning it does not change. Static IP addresses are best, because dynamic IP addresses often trigger spam filters.

Junk Mail Reporting (JMR): This is the name of Microsoft’s Feedback Loop program.

List Fatigue: A condition producing diminishing returns from a mailing list whose members are sent too many offers, or too many of the same offers, in too short a period of time.

List Hygiene: The act of maintaining a list so that hard bounces and unsubscribed names are removed from mailings. Some list owners also use an Email Change of Address service to update old or abandoned email addresses (hopefully with a permission step baked in) as part of this process.

List Purchase: The process in which a publisher or advertiser pays a list owner for full access to their email list. The publisher or advertiser would then own the list and send to it over their own system. This practice is typically frowned upon and can lead to high complaints and spam trap hits, as purchased lists are usually of poor quality.

List Rental: The process in which a publisher or advertiser pays a list owner to send its messages to that list. Usually involves the list owner sending the messages on the advertiser's behalf, and the publisher or advertiser never gains full access to the list unless those subscribers specifically opt-in to their email program. List rentals can be successful when highly targeted.

List-Unsubscribe: The List-Unsubscribe header is text you can include in the header portion of your messages, allowing recipients to see an unsubscribe button they can click if they would like to automatically stop future messages. List-Unsubscribe is currently being used by Gmail, Windows Live and Cloudmark.

MTA (Mail Transfer Agent): A Mail Transfer Agent is a server application that accepts email messages for relay or delivery to local recipients. MTAs are programs on mail servers that are responsible for routing and sometimes delivering mail.

MUA (Mail User Agent): A Mail User Agent is a client application that allows users to send and retrieve email from their computers. Common MUAs include Microsoft Outlook, Eudora and Netscape Messenger. MUA's are the component within the SMTP system that is responsible for creating email messages for transfer to an MTA. Also referred to as an "email client".

MX Record (Mail Exchange Record): An MX Record is a type of resource record in the Domain Name System (DNS) specifying how Internet e-mail should be routed using the Simple Mail Transfer Protocol (SMTP).

Open Rate: The number of HTML message recipients who opened your email, usually as a percentage of the total number of emails sent. The open rate is considered a key metric for judging an email campaign's success, but it has several problems. The rate indicates only the number of emails opened from the total amount sent, not just those that were actually delivered. Opens also can't be calculated on text emails, as it is dependant on image downloads. Also, some email clients allow users to scan message content without actually opening the message, which is falsely calculated as an open.

Opt-in: Opt-in email marketing means sending marketing messages only to people who explicitly requested them. If a customer asks for a specific piece of information, you have the permission to send that information and nothing more. To continue sending marketing emails you need the explicit permission to do so ("Please send me announcements and special offers via email", for example).

Opt-out: Email marketing that assumes a general permission to send marketing messages to everyone who has not explicitly stated that they do not want to receive such information. Spammers operate on this highly problematic premise. Opt-in email marketing, where messages are only sent to those who request them, is much more effective.

Phishing: A form of identity theft in which a scammer uses an authentic-looking email to trick recipients into giving out sensitive personal information, such as credit-card or bank account numbers, Social Security numbers and other data.

POP (Post Office Protocol): A protocol that defines an email server and a way to retrieve mail from it. Incoming messages are stored at a POP server until the user logs in and downloads the messages to their computer. While SMTP is used to transfer email messages from server to server, POP is used to collect mail with an email client from a server.

Postmaster: The person who manages mail servers at an organization. Usually the one to contact at a particular server/site to get help, information, or to log complaints.

Preview Pane: A setting that desktop and webmail email clients offer that allow users to preview content without actually clicking on the message.

Pristine Spam Traps: Email addresses created solely to capture spammers (sometimes referred to as honey pots). These email addresses were never owned by a real person, do not subscribe to email programs and of course will not make purchases. Many spam trap operators will post (seed) pristine traps across the internet on various participating websites. They are usually hidden in the background code of webpages and are acquired by a spambot scraping email addresses. If you're hitting pristine traps this typically indicates you have a bad data partner.

Read Rate: The percentage of email recipients who have marked your email as "Read" in their email client. Typically thought of as more accurate than open rate, since read rate is not dependant on image downloads.

Receiver: A generic term used to describe an Internet Service Provider or network that accepts and delivers large amounts of email.

Recycled Spam Traps: Email addresses that were once used by a real person. These email addresses are abandoned email accounts that are recycled by ISPs as spam traps. Before turning an abandoned email address into a spam trap, ISPs will return unknown user error codes for a year. Once ISPs reactivate (recycle) the abandoned email address, mail is once again allowed to be received by the email address. If you're hitting recycled spam traps this typically indicates your data hygiene process is not working.

Re-engagement Campaign: An email campaign sent to inactives, or non-responders, in an attempt to win them back and get them engaging with your emails again in the form of opens, clicks, and conversions. A re-engagement campaign can be sent to inactives as a stand-alone campaign, or as a series of campaigns.

Reply-to Address: 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.

Reputation: Sender reputation is comprised of domain and IP reputation, and is developed using a variety of metrics, including complaint rate, unknown user rate, volume, and spam trap hits. ISPs consider a sender's reputation when determining inbox vs. junk placement of emails. A sender's reputation can be tracked using Return Path's Sender Score ranking tool.

Responsive Design: Using a CSS3 coding technique called media queries, Responsive Design allows your email to automatically re-format and re-size itself to optimize for whatever screen size your recipient is using to read your email. It can also be used to hide non-essential elements of the email from the mobile reader, thus making sure the main call-to-action of the email is easily found, and can change various other elements of the email, including text size and color, background images and background color.

Return-Path: Also referred to as the "bounce address" or "envelope sender address". This is the address a message really came from, as opposed to the Friendly From Address, and it's the address to which any undeliverable message notices (bounces) are sent.

Reverse DNS (rDNS): The process in which an IP address is matched correctly to a domain name, instead of a domain name being matched to an IP address. Reverse DNS is a popular method for catching spammers who use invalid IP addresses. If a spam filter or program can't match the IP address to the domain name, it can reject the email.


Have a different definition for one of the terms above, or did I miss an important term?  Please comment below!

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