Email Deliverability Terminology Guide

Modified on Fri, 19 May 2023 at 01:45 AM

Email deliverability is a crucial aspect of email marketing that every marketer should be familiar with. It refers to the ability of an email to successfully reach the intended recipient's inbox. This article aims to provide an email deliverability glossary to help you understand the various terminologies associated with email deliverability.


A Records: Address records are referred to as A Records. They display the IP address associated with the web pages of a particular domain name. This is associated with the local domain for ESPs. For the links that are displayed in the emails that are sent, the local domain serves as the foundation. Your email programme does not have records configured. This is accomplished instead through the DNS settings that you or your hosting company control.

Allowlist: A list of elements, such as IP addresses, domain names, URLs, or usernames, that are permitted access to a certain system protocol is known as a "allowlist." This is often referred to as a "whitelist."

Authentication: This refers to the process of verifying the sender's identity and the legitimacy of the email message. Authentication helps to prevent phishing and spam emails by confirming that the email is from a legitimate source. The commonly used authentication protocols are SPF, DKIM, and DMARC.


Blacklist: A blacklist is a list of IP addresses or domains that are known to send spam or malicious emails. Email providers use blacklists to filter out spam and other unwanted emails. Being on a blacklist can significantly reduce email deliverability.

BIMI: Brand Indicators for Message Identification (BIMI) is a protocol that enables brands to validate their logo displayed in email inboxes based on the sender's DNS settings.

Block: A block occurs when an incoming email is prevented by the recipient's inbox provider. Typically, this is due to a temporary reason, such as the sender's IP address being blocklisted or an issue with the email's content.

Bots: Bots are maliciously created robots that sign up for forms in large numbers simultaneously. Although bots may resemble genuine email addresses initially, this activity is known as list bombing and is a type of cybersecurity attack.

Bulk Email: Bulk email refers to sending the same email message to a large group of recipients. Bulk email is often used for marketing campaigns, newsletters, and other promotional activities.

Bounce: A bounce occurs when an email is returned to the sender, either because the recipient's email address is invalid, or the recipient's email server has rejected the email. Bounces can be hard or soft. A hard bounce is a permanent failure, while a soft bounce is a temporary failure.


CAN-SPAM: The Controlling the Assault of Non-Solicited Pornography and Marketing (CAN-SPAM) Act is a US law that regulates commercial emails. The law requires that commercial emails include an opt-out mechanism, a valid physical address, and accurate header information.

CASL: CASL is Canada's anti-spam legislation that's similar to the CAN-SPAM Act. It regulates the types of emails that commercial senders can send to protect consumers and businesses from digital threats such as spam. It also aims to help businesses stay competitive in a global digital marketplace.

CCPA: CCPA stands for California Consumer Privacy Act, a law that came into effect on January 1, 2020. It governs how businesses handle the personal information of California residents.

CNAME: CNAME stands for canonical name and can be used to alias one name to another. For instance, if you have both and pointing to the same application and hosted by the same server, you can create an A record for pointing to the server IP address and a CNAME record for pointing to As a result, both domain names point to the same server IP address, and any changes made to the A record for automatically reflect in the CNAME record for

Click tracking: It is a URL used to collect analytics within an email. Recipients can see the tracking domain when they hover over or click a link within the email.

Clipping: Clipping happens when an email exceeds 102KB in size and is truncated by Gmail. This can lead to a sharp decrease in open rates because open events are calculated when a tracking pixel is loaded at the bottom of an email. If an email is clipped, then this open event will not register, leading to underreported open rates.


Dedicated click tracking: Dedicated click tracking enables a customer to display their domain on click tracking links instead of the default encoding. This customization can further strengthen brand awareness and engagement.

Dedicated IP address: A dedicated IP address is an IP address exclusively assigned to a single account or user. This is in contrast to a shared IP address, which multiple accounts or users may share.

Dedicated sending domain: A dedicated sending domain allows a business to use its own domain instead of a shared domain provided by an email service. This process, known as whitelabeling, enhances brand recognition and trust with customers.

Deferred: An email is deferred when a receiving inbox provider delays accepting the message. This delay could be due to technical issues with the receiving server or a high volume of spam complaints on the email. However, a deferred email can still be delivered at a later time.

Delivery: Delivery occurs when an email is successfully delivered to the correct email address and is allowed by the recipient's IP address. Even if the email is delivered to the spam folder, it still counts as a delivery.

Deliverability: Email deliverability refers to the success of an email reaching the intended inbox (including tabbed inboxes like Google's Promotions tab). An email is not successfully delivered if it ends up in the spam folder or is blocked entirely.

DKIM: DKIM (DomainKeys Identified Mail) is a cryptographic technology that ensures the authenticity of email messages. DKIM defends against malicious modifications of messages in transit, detects content tampering, and prevents the falsification of emails.

DMARC: DMARC (Domain-based Message Authentication, Reporting, and Conformance) uses SPF and DKIM to authenticate email messages and determine whether or not to accept them. DMARC unifies DKIM and SPF and provides information about forged emails sent in a sender's name.

DNS: DNS (Domain Name System) is a system that translates domain names into IP addresses to facilitate communication on the internet. DNS providers host domain names, like GoDaddy, Cloudflare, HostGator, and SquareSpace.

Domain: A domain is a unique registered name used for sending emails and other communication, like a website address.

Domain reputation: A domain reputation is a measure of the trustworthiness of a sending domain based on its sending practices and infrastructure. Inbox providers use domain reputation to determine whether to accept or reject emails from a particular domain.


Email engagement: Email engagement is the term used to describe when recipients open and/or click on the emails sent by your business. It is an important metric that inbox providers use to evaluate your sending practices.

ESP: An ESP, or email service provider, is a system that allows you to send commercial and transactional emails to your customers. 


Feedback Loop: A feedback loop is a mechanism that allows senders to receive feedback on spam complaints and other email delivery issues. Feedback loops can help senders identify and address issues that could harm email deliverability.


GDPR: The General Data Protection Regulation (GDPR) is a law that was introduced by the European Commission in 2016 and became effective on May 25, 2018. Its purpose is to safeguard the privacy rights of all EU citizens, including those who interact with businesses located outside of the European Union, by imposing strict rules around the processing of personal data.

Graymail: Graymail refers to emails that are not necessarily spam but are not essential to the recipient. Examples of graymail include newsletters, promotional emails, and social media notifications.


Hard bounce: When an email cannot be delivered permanently, such as due to an invalid email address, it's called a hard bounce. 

Header: Email header contains key identifying details about the email, such as sender and recipient addresses, subject line, date, etc.


Inbox Placement: Inbox placement refers to the ability of an email to land in the recipient's inbox rather than the spam folder. Achieving high inbox placement rates is crucial for email marketing success.

ISP: An Internet Service Provider (ISP) is a company that offers services for accessing and using the internet. Although some ISPs provide email services, their offerings may not be as feature-rich as those of email-focused providers. This differentiates them from web-hosted inbox providers such as Verizon, Xfinity, and others.

IP Reputation: IP reputation is a measure of the trustworthiness of an IP address in sending email. Email providers use IP reputation to filter out spam and other unwanted emails. A good IP reputation can improve email deliverability.


List bombing: List bombing is a malicious technique of flooding email list signup pages with a huge number of new email addresses simultaneously, as a form of attack. Although it may appear to be a spike in signups, it is actually a cyberattack.

List Hygiene: List hygiene refers to the process of keeping an email list clean and up-to-date. It involves removing invalid email addresses, unsubscribes, and inactive subscribers. Maintaining good list hygiene can improve email deliverability.


MBP: MBP stands for Mailbox Provider, which is also known as an Inbox Provider. It is a service that manages email communication, such as Outlook, Gmail, and others. MBPs are companies that provide servers for sending, receiving, accepting, and storing emails.

MX record: MX record  stands for Mail Exchanger record. It identifies the mail server responsible for handling incoming email messages for a domain name. It is a DNS resource record.

MX records work together with A records, which point to the mail server(s). When another mail server tries to communicate with your mail server, it looks for an MX record. This MX record should then point to the A record, which in turn points to the IP address of the mail server.


Open Rate: The open rate is the percentage of email recipients who opened the email. A high open rate is an indication that the email subject line and content are engaging.


Permission Pass: Permission Pass is a one-time email sent to confirm opt-in permission for recipients who haven't engaged with your messaging in a long time. To receive future emails, recipients need to open and click a CTA within the email to confirm their subscription. If they don't click, they are either suppressed or removed from your email list. You can engage these recipients through other marketing channels to encourage them to resubmit an email signup form on your website.

Pristine Spam Trap: A Pristine Spam Trap (PST) is specifically designed to identify senders who are sending spam or not following the best sending practices. These are brand new email addresses that are never used for real-world instances. If you hit a PST, it can lead to your IP being blocklisted or your emails being marked as spam. In the eyes of mailbox providers, this indicates that you either purchased a list or do not follow the best practices since these addresses are not legitimate and do not open emails.


Ramping: Ramping is the process of gradually increasing the email quantity in order to build a positive reputation as a sender, which is important for both domain and IP addresses. Customers with a new domain must warm their domain.

Reputation Monitoring: Reputation monitoring refers to the process of monitoring sender reputation, IP reputation, and domain reputation to identify and address any issues that could affect email deliverability.


Sending domain: The sending domain refers to the registered name on the internet (e.g.,

Sender Policy Framework (SPF): SPF is an email authentication protocol that verifies that the sender is authorized to send emails on behalf of a domain. SPF helps to prevent email spoofing and improve email deliverability.

Sender reputation: The sender reputation is a measure of how trustworthy an email sender is perceived to be by inbox providers, based on their sending practices and infrastructure. It is a critical factor in determining the placement of an email, such as spam, promotions, or primary.

Seed List: A seed list is a list of email addresses that are used to monitor email deliverability. Seed lists are often used to test email campaigns before sending them to the entire email list.

Shared IP address: A shared IP address is an IP address that multiple email senders use to send their emails. This is often done to reduce costs and can be used by both reputable and disreputable senders.

Shared sending domain: A shared sending domain is a root domain shared by multiple accounts. 

Soft bounce: A soft bounce is a temporary failure to deliver an email due to reasons like the recipient's inbox being full or the email server being down.

SPF: SPF stands for Sender Policy Framework, which is a security measure that verifies the authenticity of the sender of an email. SPF records are added to the DNS and specify which IP addresses are authorized to send emails on behalf of the domain.

Spam: Spam refers to unsolicited bulk email sent to a large number of recipients, often for commercial or malicious purposes.

Spam complaint: A spam complaint occurs when an email recipient actively marks an email as spam. This is different from when an email ends up in the spam folder without any action taken by the recipient.

Spam trap: A spam trap is an email address or domain used to detect and monitor unsolicited emails. It is often used by mailbox providers, ISPs, or other organizations to identify senders who do not follow best practices or use illegal tactics to send emails.

Spoofing: Email spoofing is a technique used by phishers to modify the email header to make it appear as if the email was sent from someone else. It is often used to trick recipients into providing personal information or login credentials.

Subdomain: A subdomain is an extension of the main domain and is often used as a prefix in a sending domain (e.g.

Suppress: When a contact is suppressed, they can no longer be contacted. This can occur due to reasons like unsubscribing, marking an email as spam, hard bouncing, soft bouncing 7+ times in a row, or being manually suppressed.

Suppression List: A suppression list is a list of email addresses that have opted-out or bounced and should not receive any further emails from the sender. Suppression lists are often used to maintain good list hygiene and improve email deliverability.


TINS: TINS refers to emails that recipients retrieve from their spam folder by marking them as "This Is Not Spam." By doing so, the inbox provider is notified that the user wants to receive those emails.

TXT Record: A TXT record (Text Record) is a type of DNS record that holds free-form text of any kind. Its primary use is to verify the authenticity of emails, but it has also been used to store human-readable information about servers, networks, data centers, and other accounting data. A fully qualified domain name may have multiple TXT records, with the most common uses being SPF, DKIM, DK, and DMARC.


Unsubscribe: An unsubscribe is a mechanism that allows recipients to opt-out of receiving future emails from a sender. Every commercial email must include a clear and conspicuous unsubscribe mechanism that allows recipients to easily opt-out.


Warming: Warming is the process of establishing a good sending reputation when starting to send email. It's important for dedicated IP and sending domains. It involves turning on high engagement flows, sending campaigns to highly engaged recipients, monitoring engagement, and adjusting accordingly.

Whitelist: A whitelist is a list of email addresses or domains that are allowed to bypass spam filters and reach the recipient's inbox. Whitelisting can improve email deliverability and ensure that important emails are not filtered out as spam.

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