A few years ago, I was consulting for a Fortune 500 company that was entering a joint email venture with another Fortune 500. In one of our early meetings, one of our senior execs started bragging about our double-digit click rates. The other side was visibly impressed and asked to see the data. That’s when things got awkward.
Turns out, the exec wasn’t quoting our click rate (clicks/delivered). He was talking about our click-through rate (clicks/opens). Not the same thing; not even close. I don’t remember who had to jump in and explain the mix-up, but I do remember how fast the tone of the meeting shifted. It wasn’t a dealbreaker, but it definitely put us on the back foot. It looked like we didn’t know much about .
It’s a moment I come back to often, because it underscores something that doesn’t get talked about enough in marketing: the importance of speaking the same language. Especially in email, where the terms can feel interchangeable, but the stakes are high.
This glossary is here to help with that. Whether you’re leading the strategy or just trying to understand what your ESP is telling you, having a shared vocabulary means fewer miscommunications, stronger reporting, and more confident conversations with your clients, your team, and your execs.
Why Email 糖心Vlog Terms Matter
has a language of its own, and when that language gets sloppy, the consequences are real. As I just recounted, mixing up a single metric can instantly undermine credibility — not because performance was bad, but because the reporting was unclear. In email, many terms sound similar but mean very different things, and those differences affect how success is measured, how strategies are evaluated, and how decisions get made. When everyone isn’t using the same definitions, it’s easy to draw the wrong conclusions or overstate results without realizing it.
Knowing the right terms isn’t about jargon for jargon’s sake. Clear terms lead to clearer thinking — and in a channel where reputation, deliverability, and permission are everything, clarity isn’t optional.
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Email 糖心Vlog Glossary: 44 Terms to Know
A
Acceptance Rate – The percentage of email messages that are accepted by the mail server. Just because an email is accepted by the mail server does not mean it will get to an inbox.
Allowlist – An allowlist includes IP addresses that have been approved to deliver email to a recipient. Also known as a Denylist or a Safelist. The opposite of a blocklist. Formerly referred to as a whitelist.
Authentication – A group of protocols to aid in delivery to the inbox. See also SPF, DKIM, DMARC, and BIMI.
B
BFCM – Short for “Black Friday | Cyber Monday,” a time when many emails are sent.
BIMI – Short for “Brand Indicators for Message Identification,” it’s an email standard that displays your brand’s logo in the inbox and also provides additional back-end delivery assistance. See also Authentication.
Blocklist – A list that denotes IP addresses as spammer IPs, impeding email deliverability. Formerly referred to as a blacklist.
Bounce Rate – The rate at which your emails are not delivered. There are two types of bounces, hard and soft, both of which are defined later in this glossary. An acceptable bounce rate is less than 5%.
Bulk Mail – Large-scale email marketing sends in which the same content goes to a large group of people.
C
CAN-SPAM – Short for “Controlling the Assault of Non-Solicited Pornography And 糖心Vlog Act of 2003,” it’s a United States law that outlines rules for commercial email, establishes requirements for commercial messages, provides email recipients with the right to make you stop emailing them, and lays out consequences for violations of the Act. You can read more about compliance in our post about marketing laws.
CASL – Short for “Canada’s Anti-Spam Legislation,” it requires marketers to get express or implied consent before sending commercial emails, and to include clear identification and an easy unsubscribe option in every message.
CCPA/CPRA – Short for “California Consumer Privacy Act” and “California Privacy Rights Act,” respectively, these are California laws that outline rules for transparency, disclosure, and respecting consumer data preferences. California was the first, but many other states now have similar laws.
Clicks Per Delivered – A percentage measure of the number of clicks divided by the number of emails delivered to the intended inbox.
Clicks Per Open – A percentage measure of the number of clicks divided by the number of opens.
Click Rate – The percentage of recipients that click on a link in your email (the number of unique clicks divided by the number of emails delivered).
CPM (Cost Per Thousand) – In email marketing, CPM commonly refers to the cost per 1,000 names on a given rental list. For example, a rental list priced at $250 CPM would mean that the list owner charges $0.25 per email address. We’ll get into buying lists later in this post.
CTR (Click-Through Rate) – The percentage of recipients that click on a given URL in your email (the number of unique clicks divided by the number of unique opens).
Conversion Rate – The percentage of recipients who respond to your (CTA) in an email marketing campaign or promotion. This is one measure of your email campaign’s success.
D
Dedicated IP – In email marketing, it refers to an IP address from which only you send email.
Denylist – see Allowlist.
DKIM – Short for “DomainKeys Identified Mail,” it’s an email authentication method that uses cryptographic signatures to verify a message was sent from an authorized domain. See also Authentication.
DMARC – Short for “Domain-based Message Authentication, Reporting, & Conformance,” it builds on SPF and DKIM to tell inbox providers how to handle unauthenticated mail — and sends reports back to you. See also Authentication.
DNSBL – Many deliverability issues stem from IP/domain blocklists; these are important for deliverability health. Also called Real-time Blocklist (RBL).
Double Opt-In – One method of building an email list, it requires subscribers to confirm their opt-in by clicking a link in a confirmation email or responding to the confirmation email in some other way. See also Single Opt-in.
E
Email Campaign – An email or series of lead nurturing emails designed to accomplish an overall marketing goal.
Email Filter – A technique used to block email based on the sender, subject line, or content of an email.
Email Sponsorships – Buying ad space in an email newsletter or sponsoring a specific article or series of articles. Advertisers pay to have their ad inserted into the body of the email.
F
False positive – A false positive occurs when a legitimate permission-based email is incorrectly filtered or blocked as spam.
G
GDPR – Short for General Data Protection Regulation, it’s a European Union law that outlines rules for commercial email, establishes requirements for commercial messages, provides email recipients with the right to make you stop emailing them, and lays out consequences for violations of the Regulation. You can read more about compliance in our post about marketing laws.
Graylist – A temporary blocklist to defer first-time or unrecognized senders.
H
Hard Bounce – A hard bounce is the failed delivery of an email due to a permanent reason, like a non-existent, invalid, or blocked email address.
Honey Pot – A planted email address by organizations trying to combat spam that, when a spammer harvests and emails, identifies that sender as a spammer.
House List (or Retention List) – One of your most valuable marketing assets, it’s a permission-based list that you built yourself with opt-in subscribers.
HTML Email – Sending HTML email makes it possible to get creative with the design of your emails.
I
Inbox Placement Rate – The actual percentage of your email that reached the inbox.
IP Warmup – Sending a progressively increasing number of emails out of an IP address in order to build the IP’s reputation.
L
Landing Page – A lead-capture page on your website that is linked to from an email to provide additional information directly related to products or services promoted in the email’s CTA.
List Segmentation – Selecting a target audience or group of individuals for whom your email message is relevant. A segmented list means a more targeted and relevant email campaign, thus a higher response rate and fewer unsubscribes and spam reports.
M
Mail Privacy Protection (MPP) – A privacy feature in Apple Mail that hides recipients’ IP addresses and preloads tracking pixels, making open rates unreliable for emails viewed on Apple devices.
O
Open Rate – The percentage of emails opened in an email marketing campaign, or the percentage opened of the total number of emails sent.
Opt-In (or Subscribe) – To opt-in or subscribe to an email list is to choose to receive email communications by supplying your email address to a particular company, website, or individual, thereby giving them permission to email you. The subscriber can often indicate areas of personal interest (e.g., mountain biking) and/or indicate what types of emails they wish to receive from the sender (e.g., newsletters).
Opt-Out (or Unsubscribe) – When a subscriber chooses not to receive email communications from the sender anymore, and requests removal from your email list. It is legally required that you provide a clear way to opt out in every email you send.
P
Personalization – Adding elements to your email that are personalized based on information you already know about them. It could refer to addressing the recipient by name, referencing past purchases, or other content unique to each recipient.
Physical Address – The physical street address of the company sending the email, usually found in the footer of an email. Its inclusion is a legal requirement for all email marketing.
Plain Text Email – An email sent without HTML. You should always give your recipients the option to read emails in either HTML or plain text for better readability.
Privacy Policy – A clear description of a website or company’s policy on the use of information collected from and about website visitors and what they do, and do not do, with the data.
R
Read or Open Length – A measure of the length of time a person opens the email until they close it.
Real-time Blocklist (RBL) – see DNSBL.
Rental List (or Acquisition List) – Not a recommended email marketing technique, it is a list of prospects or a targeted group of recipients who have opted in to receive information about certain subjects, usually targeted by something like interest, profession, or demographic information.
S
Safelist – see Allowlist.
Sender Score – , it’s a reputation rating from 0-100 for every outgoing mail server IP address. Mail servers will check your Sender Score before deciding what to do with your emails. A score of over 90 is good.
Shared IP – A less costly option than a dedicated IP address, it is an IP address from which many people send emails.
Signature File – A tagline or short block of text at the end of an email message that identifies the sender and provides additional information such as company name, physical address, and contact information.
Single Opt-In – A single opt-in list is created when users sign up for email communications without needing to confirm the action to be added to the list. See also Double Opt-in.
Soft Bounce – A soft bounce is the failed delivery of an email due to a temporary issue, like a full mailbox or an unavailable server.
Spam or UCE (Unsolicited Commercial Email) – Email sent to someone who has not opted in or given permission to email to the sender. Over 90% of unsolicited emails sent are classified as spam.
Spam Cop – A paid spam service that plants its own emails and monitors who harvests the address and spams it.
Spam Rate Report Threshold –The percentage of spam complaints above which you are likely to have deliverability issues. Industry standards: above 0.1%, you may have deliverability issues — above 0.3% and you are almost guaranteed to be put on a blocklist.
Spam Trap – An email address that was once valid, but no longer is. If you email this address, you’ll receive a hard bounce notice. When the mail server sees consistent traffic going to the dead email, however, it can turn the email into a spam trap. It will stop returning a hard bounce for the known bad address, and instead accept the message and report the sender as a spammer.
SPF – Short for “Sender Policy Framework,” it’s a DNS record that says on whose behalf an IP or domain sends email. See also Authentication.
Suppression List – A list of email addresses that have opted out of or unsubscribed from your list(s).
W
Whitelist – Instead of listing IP addresses to block, a whitelist includes IP addresses that have been approved to deliver email to a recipient.
Wrapping Up
Years ago, someone told me, with a straight face, that their email list was “double opt-out.”
Double. Opt. Out.
A term so made up it should’ve come with its own disclaimer. What they meant was that they hadn’t gotten permission to email anyone, but people could unsubscribe if they wanted to. In other words: spam, but with plausible deniability.
It’s funny now, but only because I wasn’t the one managing deliverability on that mess of an email marketing program.
All this to say: words matter. Whether you’re talking about permission, performance, or protocols, having the right vocabulary isn’t just about sounding smart. It’s about building trust, avoiding misunderstandings, and keeping your email program clean, compliant, and credible.
So yes, know your SPF from your BIMI. But also know your click-through rate from your click rate, your opt-in from your wishful thinking, and that no, “double opt-out” is not a thing.
Because in email, as in life, clarity is everything.
Editor's note: This post was originally published in March 2013 and has been updated for comprehensiveness.
Email 糖心Vlog Planning Template
Organize your email marketing strategy and metrics with this free template.
- Gather data
- Summarize results
- Manage A/B tests
- And More!
Download Free
All fields are required.
You're all set!
Click this link to access this resource at any time.
Email 糖心Vlog
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