{"id":5825,"date":"2024-12-13T16:07:57","date_gmt":"2024-12-13T21:07:57","guid":{"rendered":"https:\/\/www.litmus.com\/blog\/27-deliverability-terms-every-email-marketer-should-know\/"},"modified":"2026-02-06T14:58:09","modified_gmt":"2026-02-06T19:58:09","slug":"email-deliverability-glossary","status":"publish","type":"post","link":"https:\/\/www.litmus.com\/blog\/email-deliverability-glossary","title":{"rendered":"A Comprehensive Glossary of Email Deliverability Terms"},"content":{"rendered":"\n\n\t<div id=\"simple-text-block-block_964a3513ce3a84eccb0f42561f8d6443\" class=\"block-simple-text-block alignfull \" style=\"background-color:\">\n  <div class=\"container\">\n  \t<div class=\"row\">\n  \t\t<div class=\"col\">\n  \t\t\t<div class=\"copy\">\n  \t\t\t\t<p><span style=\"font-weight: 400;\">You invest so much time and effort into creating emails that drive brand awareness, engage subscribers, and encourage your audience to take action and convert. But if your email never hits the inbox, all that hard work can be for nothing.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">While <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/email-deliverability-facts\/\"><span style=\"font-weight: 400;\"><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/email-deliverability\">email deliverability<\/a> can be a bit of a mystery, <\/span><\/a><span style=\"font-weight: 400;\">understanding some of the more technical terms that play into it can make it a little less daunting. If you\u2019re looking for how to fix your email deliverability, you get stuck on all the acronyms to keep track of: DMARC, DKIM, SPF\u2026what does it all mean?<\/span><\/p>\n<p><span style=\"font-weight: 400;\">To help, we\u2019ve created <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/wp-content\/uploads\/pdf\/33-Email-Deliverability-Terms-to-Know.pdf\"><span style=\"font-weight: 400;\">this cheat sheet of 33 email deliverability terms <\/span><\/a><span style=\"font-weight: 400;\">that you can keep on hand for easy reference. Print one of these out and stick it right above your desk\u2014so you\u2019ll never mix up soft bounces and hard bounces again.<\/span><\/p>\n  \t\t\t<\/div>\n  \t\t<\/div>\n  \t<\/div>\n  <\/div>\n<\/div>\n\n\n<div id=\"post-cta-buttonblock_a4da1e8bb9f5f8007b8666601e5eb0b8\" class=\"block-post-cta-button mt-5\">\n  <div class=\"container px-0\">\n    <div class=\"row\">\n      <div class=\"blog-post-cta-button-wrapper col-12 col-lg-10 mx-auto p-4 d-block d-lg-flex align-items-lg-center align-items-start\">\n\t\t  \t\t  \t\t  \t\t  \t\t  \t\t  \t\t  \t\t \t\t\t  \t\t  \t\t  <div class=\"col-12 col-lg-9 ps-lg-4 ps-0 text-center text-lg-start mt-3 mt-lg-0\">\t\t\t  \t\t\t  <h2 class=\"h-sm\"><strong>Unlock 2025 inbox benchmarks now<\/strong><\/h2>\n\t\t\t   \n\t\t\t  \t\t\t\t\t<p>Download Validity\u2019s 2025 Email Deliverability Benchmark Report and learn how your inbox placement compares before your next send.<\/p>\n\t\t\t\t\t \n\t\t\t  \t\t  <\/div><!--col-12 col-lg-9 ps-lg-4 ps-0 text-center text-lg-start mt-3 mt-lg-0-->\t\t\t  \t\t  <div class=\"text-center text-lg-end col-12 col-lg-1 ms-lg-2 ms-0\">\n\t\t\t\t\t\t\t\t\t\t<a class=\"btn btn-primary\" rel=\"noopener\" target=\"_blank\" href=\"https:\/\/www.validity.com\/resource-center\/2025-email-deliverability-benchmark-report\/\">\n\t\t\t\t\t\tGET THE REPORT\t\t\t\t\t\t<\/a>\n\t\t\t  \t\t  <\/div><!--text-center text-lg-end col-12 col-lg-1 ms-lg-2 ms-0-->\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t        <\/div><!--blog-post-cta-button-wrapper-->\n    <\/div><!--row-->\n  <\/div><!--container-->\n<\/div>\n\n\n\n\t<div id=\"simple-text-block-block_2c4ce58965547d532e57456eeea2f42f\" class=\"block-simple-text-block alignfull \" style=\"background-color:\">\n  <div class=\"container\">\n  \t<div class=\"row\">\n  \t\t<div class=\"col\">\n  \t\t\t<div class=\"copy\">\n  \t\t\t\t<p>&nbsp;<\/p>\n<p><span style=\"font-weight: 400;\">If you\u2019re stumped on a certain term, click a link below to take you straight to it and related terms:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><a rel=\"noopener\" href=\"#email-deliverability\"><span style=\"font-weight: 400;\">What is email deliverability?<\/span><\/a><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><a rel=\"noopener\" href=\"#sender-reputation\"><span style=\"font-weight: 400;\">Sender reputation and authentication<\/span><\/a><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><a rel=\"noopener\" href=\"#performance-behavior\"><span style=\"font-weight: 400;\">Email performance and subscriber behavior<\/span><\/a><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><a rel=\"noopener\" href=\"#list-hygiene\"><span style=\"font-weight: 400;\">List management and hygiene<\/span><\/a><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><a rel=\"noopener\" href=\"#email-faq\"><span style=\"font-weight: 400;\">Email deliverability FAQs<\/span><\/a><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Otherwise, study up\u2014this is your comprehensive guide to email deliverability terms:<\/span><\/p>\n<h2><span id=\"email-deliverability\" style=\"font-weight: 400;\">What is email deliverability?<\/span><\/h2>\n<p><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/why-email-deliverability-matters\"><span style=\"font-weight: 400;\">Email deliverability<\/span><\/a><span style=\"font-weight: 400;\"> is a measure of whether or not the email messages you send make it to your subscriber\u2019s inbox rather than the spam folder. Deliverability refers to inbox placement. Does the message go to a folder like Gmail\u2019s Promotional Tab, the primary inbox, or to spam?<\/span><\/p>\n<p><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/the-difference-between-deliverability-and-delivery-rate\"><span style=\"font-weight: 400;\">Email deliverability is different from email delivery<\/span><\/a><span style=\"font-weight: 400;\">, which refers to whether or not a receiver (mailbox provider) accepts the message you\u2019ve sent. You can have great email delivery (all of your emails arrive in a subscriber\u2019s mailbox) but poor deliverability (and they all landed in the spam folder, womp womp.)\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Several factors influence your deliverability, starting with your sender reputation and authentication.<\/span><\/p>\n<h2><span id=\"sender-reputation\" style=\"font-weight: 400;\">Sender reputation and authentication<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">Investing in your email-sending infrastructure helps <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/how-to-fix-email-reputation\/\"><span style=\"font-weight: 400;\">build a better sender reputation<\/span><\/a><span style=\"font-weight: 400;\">, which boosts your credibility when sending emails. That includes:<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">IP Reputation<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Internet Protocol (IP) addresses uniquely identify you and your server. Every computer has one, including the one (or the smartphone) you\u2019re reading this blog post on right now.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Your IP reputation is attributed to an IP address based on what metrics an inbox service provider (ISP) has historically seen from that IP address and how users engage with mail that originates from it.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Domain Reputation<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Your domain refers to locations of servers and devices connected to the internet. Domain names can represent a whole bunch of different IP addresses. For example, the domain www.litmus.com would address the collection of servers that host our website. Whether that is <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/\"><span style=\"font-weight: 400;\">www.litmus.com\/blog<\/span><\/a><span style=\"font-weight: 400;\"> or <\/span><a rel=\"noopener\" href=\"https:\/\/litmus.com\/community\/discussions\"><span style=\"font-weight: 400;\">www.litmus.com\/community<\/span><\/a><span style=\"font-weight: 400;\">, the domain is the same.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Because email isn\u2019t always sent from just one IP address or provider, ISPs also use your sending domain to track reputation. That allows a receiver to accumulate a reputation score across the board.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Sender Policy Framework (SPF)<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">SPF (pronounced \/\u02cces.pi\u02d0\u02c8ef\/) allows mail services to double check that incoming mail from a specific domain has, in fact, been sent from that domain. SPF protects the envelope sender address, or return path, by comparing the sending mail server\u2019s IP address to a master list of authorized sending IP addresses as part of the DNS Record.\u00a0<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">DomainKeys Identified Mail (DKIM)\u00a0<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">DKIM (pronounced \/\u02c8di\u02d0\u02cck\u026am\/) allows your organization to claim responsibility for your email. It\u2019s an identifier that shows your email is associated with your domain and uses cryptographic techniques to make sure it should be there.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Domain-Based Message Authentication, Reporting, and Conformance (DMARC)\u00a0\u00a0<\/span><\/h3>\n<p><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/dmarc-what-it-is-how-it-helps-protect-your-brand-against-email-fraud\"><span style=\"font-weight: 400;\">DMARC<\/span><\/a><span style=\"font-weight: 400;\"> (pronounced \/\u02c8di\u02d0\u02c8m\u00e4rk\/) gives you insight into the abusive senders that may be impersonating you and can help you identify them. It allows a sender to indicate that an email is protected by SPF or DKIM. The sender can then receive a report back on any messages that failed the authentication and identify if anyone using the domain could be a spammer.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Brand Indicators for Message Identification (BIMI)<\/span><\/h3>\n<p><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/what-is-bimi-and-why-should-email-marketers-care\"><span style=\"font-weight: 400;\">BIMI<\/span><\/a><span style=\"font-weight: 400;\"> (pronounced \/\u02c8bi.mi\/) is a text record that is used to verify information about your brand that works right alongside SPF, DMARC, and DKIM. It signals to email clients that you are you. What makes BIMI extra interesting for email marketers is that verifying with BIMI can unlock brand imagery in the inbox and\/or a blue verified checkmark, depending on the email client, which adds credibility to your messages and can (theoretically) increase your open rates.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">DNS Record<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">The domain name system (DNS) is a naming database where your domain name is located and translated into an IP address. Basically, it\u2019s where all of your authentication protocols live.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">MX (Mail Exchange) Records<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">A DNS Mail Exchange (MX) record tells mail servers where to direct an email message in accordance with the Simple Mail Transfer Protocol (SMTP). This is the back-end magic that connects your message to the right email address. Failure to configure your MX record correctly could result in a higher bounce rate or delivery issues, which in turn impact your deliverability.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">IP Warming<\/span><\/h3>\n<p><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/ip-domain-email-warm-up\"><span style=\"font-weight: 400;\">IP warming <\/span><\/a><span style=\"font-weight: 400;\">is the process of slowly increasing the volume of email you send from a new domain or IP address. Whether you\u2019re switching to a new email service provider (ESP), getting started sending emails for the first time, or going through a merger or acquisition, IP warming can help maintain your deliverability.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">This gives ISPs time to evaluate your authentication protocols, content, and infrastructure to determine that you\u2019re a legitimate sender. As you establish your sender reputation, you can ramp up to your normal send volume.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">DNS Pointer Record (PTR Record)<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">DNS PTR Records help you match IP addresses to sender domain names. When you run a reverse DNS lookup with your IP address, the PTR record finds the domain name. (This is the opposite of an \u201cA\u201d record, which gives you the IP addresses associated with a given domain name.)\u00a0<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Greylisting<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Greylisting is an email security practice mail servers use to protect their users from senders they haven\u2019t received mail from before. Rather than completely block your message, your email will be temporarily rejected.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The logic is that if the mail is legitimate, the originating server will try again to deliver the message after a delay, at which time the email will be accepted. A spammer wouldn\u2019t take the time to retry sending an email as they\u2019re going through thousands of email addresses.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Email Sender Reputation<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">All of this adds up to your <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/how-to-fix-email-reputation\"><span style=\"font-weight: 400;\">email sender reputation<\/span><\/a><span style=\"font-weight: 400;\">, which is a score that ISPs assign to an organization that sends emails. ISPs evaluate your sender behavior (the volume of emails you send, and how often you send them), your infrastructure (the authentication measures you take to keep your subscribers safe), and your subscriber behavior (your email marketing performance and subscriber engagement) to determine your sender reputation.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The better your reputation, the more likely you\u2019ll have a higher <a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/why-email-deliverability-matters\" target=\"_blank\">email deliverability<\/a> score.<\/span><\/p>\n\n<div class=\"container pt-3 pb-5\">\n\t<div class=\"row blog-cta-blue  p-4\">\n\t\t<div class=\"col-12 mx-auto\">\n\t\t\t<div class=\"row d-flex align-items-center\">\n\t\t\t<div class=\"col-lg-6 col-12\">\n\t\t\t\t<p class=\"bold fs-4\">Monitor your sender reputation<\/p>\n\t\t\t\t<p>Stay ahead of blocklists, spam complaints, and MBP blocks with Validity Everest\u2019s real-time reputation monitoring.<\/p>\n\t\t\t\t<button class=\"button-blue arrow\"><a rel=\"noopener\" target=\"_blank\" href=\"https:\/\/www.validity.com\/everest\/reputation-monitoring\/\" class=\"text-white text-decoration-none\">Protect your reputation<\/a><\/button>\n\t\t\t<\/div><!--col-6-->\n\t\t\t<div class=\"col-6 d-none d-lg-block\">\n\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.litmus.com\/wp-content\/uploads\/2024\/12\/blog-cta-12172024.svg\" width=\"208\" height=\"171\" alt=\"\">\n\t\t\t<\/div><!--col-6-->\n\t\t\t<\/div> <!--row-->\n\t\t<\/div><!--col-12-->\n\t<\/div><!--row-->\n<\/div><!--container-->\n\t\n\t\t\n\t\n\t\n\t\n\n<h2><span id=\"performance-behavior\" style=\"font-weight: 400;\">Email performance and subscriber behavior<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">Setting up your authentication infrastructure is a must-do for your deliverability because it\u2019s directly tied to email performance and how subscribers respond to your emails. Mailbox providers want to see that subscribers open, read, and engage with your emails. Here\u2019s what you should look for:<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Open Rate<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Open rate is usually the first metric that email marketers look at to determine the success of their email campaigns. Open rate measures how many of your delivered emails were opened. While this can be a useful indicator of your subject line and preview text performance, changes like <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/measure-email-marketing-success\"><span style=\"font-weight: 400;\">Apple\u2019s Mail Privacy Protection (MPP)<\/span><\/a><span style=\"font-weight: 400;\"> make open rates a less reliable success metric.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Click-Through Rate (CTR)<\/span><\/h3>\n<p><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/increase-email-ctr\"><span style=\"font-weight: 400;\">Your click-through rate (CTR)<\/span><\/a><span style=\"font-weight: 400;\"> determines how many clicks your emails received. You can calculate click-through rate by dividing the number of emails clicked by the number of emails delivered. Taking opens out of the equation gives you a more accurate picture of email engagement.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">This is often confused with click-to-open rate (CTOR), which measures how many of your opened emails received clicks. This is a better indicator of how your subject line and preview text perform, versus your overall engagement.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Rendering Issues<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Rendering issues occur when email clients change the display of how your email appears\u2014<\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/a-guide-to-rendering-differences-in-microsoft-outlook-clients\"><span style=\"font-weight: 400;\">Outlook, we\u2019re looking at you<\/span><\/a><span style=\"font-weight: 400;\">\u2014that make it difficult or impossible to interact with. While rendering issues happen to the best of us, they can make your email campaigns look a <\/span><i><span style=\"font-weight: 400;\">little <\/span><\/i><span style=\"font-weight: 400;\">spammy to ISPs. (And depending on how wonky things get, your subscriber won\u2019t be able to engage much with your email, either, which doesn\u2019t help your deliverability.) That\u2019s why we always recommend <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/email-testing\"><span style=\"font-weight: 400;\">testing your email <\/span><\/a><span style=\"font-weight: 400;\">before you send it.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">User Engagement<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Engagement refers to how your subscribers view and interact with your emails. Think of your <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/measure-email-marketing-success\"><span style=\"font-weight: 400;\">user engagement metrics<\/span><\/a><span style=\"font-weight: 400;\"> as that sweet spot in the middle of the funnel, which includes open rate, click rate, and read time. ISPs look at your user engagement to determine your inbox placement\u2014the more your subscribers interact with your emails, the better your deliverability will be.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Unsubscribe Rate<\/span><\/h3>\n<p><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/the-ultimate-guide-to-list-unsubscribe\"><span style=\"font-weight: 400;\">Unsubscribe rate<\/span><\/a><span style=\"font-weight: 400;\"> measures how many people opt-out of your emails. Depending on your email platform, an \u201cunsubscribe\u201d could be if someone actually opts out or if they click your unsubscribe link but don\u2019t follow through. <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/new-yahoo-gmail-email-deliverability-rules\"><span style=\"font-weight: 400;\">New deliverability guidelines from Yahoo and Gmail<\/span><\/a><span style=\"font-weight: 400;\"> require one-click unsubscribes and that you process these requests in 48 hours or less.\u00a0<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Feedback Loop (FBL)<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Feedback loops allow the sender to receive a report every time a recipient clicks on the \u201cmark as spam\u201d or \u201cjunk\u201d button. Subscribing to feedback loops and using this data to quickly remove folks who are no longer interested in your email helps maintain a positive reputation.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Spam Complaints\u00a0<\/span><\/h3>\n<p><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/why-emails-go-to-spam-instead-of-inbox\"><span style=\"font-weight: 400;\">A spam complaint<\/span><\/a><span style=\"font-weight: 400;\"> is when a recipient marks your email as spam. This is an example of negative engagement\u2014you\u2019re probably not a spammer, but for whatever reason, your subscriber doesn\u2019t want to see your emails anymore. This is why it\u2019s so important to make it easy for subscribers to unsubscribe. While no one likes a high unsubscribe rate, a high spam complaint is much worse for your overall deliverability. To comply with <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/new-yahoo-gmail-email-deliverability-rules\"><span style=\"font-weight: 400;\">Gmail and Yahoo\u2019s new deliverability rules,<\/span><\/a><span style=\"font-weight: 400;\"> you should keep your spam complaints to less than 0.3%.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Bounce Rate<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">The email bounce rate is how many of your sent emails weren\u2019t delivered. This can be for temporary reasons like a too-full inbox (soft bounces) or permanent reasons like an incorrect email address (hard bounces). A high bounce rate is a sign of poor list hygiene or a<\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/the-5-most-problematic-subscriber-acquisition-sources-are-they-redeemable\"><span style=\"font-weight: 400;\"> problem with your acquisition practices<\/span><\/a><span style=\"font-weight: 400;\">. If you\u2019re seeing a bounce rate above 2%, address this problem asap as it has a big impact on your email deliverability. There are two types of bounces, a <a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/whats-the-difference-between-a-hard-and-soft-bounce\" target=\"_blank\">hard bounce vs soft bounce<\/a>:<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Soft Bounce<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">When an email bounces, it means that it never makes it to your subscriber\u2019s mailbox. (In other words, it\u2019s a delivery issue, not just a deliverability issue.) A <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/whats-the-difference-between-a-hard-and-soft-bounce\"><span style=\"font-weight: 400;\">soft bounce<\/span><\/a><span style=\"font-weight: 400;\"> means that the recipient exists, but for whatever reason, they couldn\u2019t receive your message. Soft bounces typically indicate temporary delivery issues. When a soft bounce happens, keep an eye on that email address\u2014you don\u2019t have to do anything yet, but if it keeps bouncing, you may need to clean it from your email list.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Hard Bounce<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Unlike soft bounces, hard bounces require immediate action. <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/whats-the-difference-between-a-hard-and-soft-bounce\"><span style=\"font-weight: 400;\">Hard bounces<\/span><\/a><span style=\"font-weight: 400;\"> occur when the receiving server is either unable to deliver or rejects the message. It can also occur when there is no mail server at that address, or the domain doesn\u2019t exist at all. A hard bounce indicates a permanent reason that an email can\u2019t be delivered, so you should remove them from your email list.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Inbox Placement Rate (IPR)<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Inbox placement rate shows the percentage of emails that get delivered to a subscriber\u2019s primary inbox, rather than the spam folder or other folders like Gmail\u2019s Promotions Tab.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">It\u2019s important to track all of these metrics when thinking about your deliverability. But if you were going to pick one to focus on, it\u2019s your inbox placement rate (IPR).\u00a0<\/span><span style=\"font-weight: 400;\">These are just a snapshot of the metrics you should evaluate for your email marketing strategy. Check out our full list of <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/the-email-metrics-marketers-measure-and-the-ones-they-should\"><span style=\"font-weight: 400;\">email marketing metrics<\/span><\/a><span style=\"font-weight: 400;\"> to help you measure the impact of your emails.<\/span><\/p>\n<h2><span id=\"list-hygiene\" style=\"font-weight: 400;\">List management and hygiene<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">Deliverability starts with your email list. Email marketers must balance acquisition pressure\u2014the goal shouldn\u2019t be to grow your email list with just any email addresses you can find, but rather build an audience of subscribers that care about what you have to say. Here are a few terms you need to know as you go through your email list management:<\/span><\/p>\n\n<div class=\"container pt-3 pb-5\">\n\t<div class=\"row blog-cta-blue  p-4\">\n\t\t<div class=\"col-12 mx-auto\">\n\t\t\t<div class=\"row d-flex align-items-center\">\n\t\t\t<div class=\"col-lg-6 col-12\">\n\t\t\t\t<p class=\"bold fs-4\">Clean lists. Better results.<\/p>\n\t\t\t\t<p>Remove risky and inactive addresses with Validity Everest\u2019s list validation to protect your sender reputation.<\/p>\n\t\t\t\t<button class=\"button-blue arrow\"><a rel=\"noopener\" target=\"_blank\" href=\"https:\/\/www.validity.com\/everest\/list-validation\/\" class=\"text-white text-decoration-none\">Validate lists<\/a><\/button>\n\t\t\t<\/div><!--col-6-->\n\t\t\t<div class=\"col-6 d-none d-lg-block\">\n\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.litmus.com\/wp-content\/uploads\/2024\/12\/blog-cta-12172024.svg\" width=\"208\" height=\"171\" alt=\"\">\n\t\t\t<\/div><!--col-6-->\n\t\t\t<\/div> <!--row-->\n\t\t<\/div><!--col-12-->\n\t<\/div><!--row-->\n<\/div><!--container-->\n\t\n\t\t\n\t\n\t\n\t\n\n<h3><span style=\"font-weight: 400;\">List Hygiene<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">List hygiene, or list management, is the practice of maintaining an email list of subscribers that actually want to hear from you. <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/email-list-hygiene-how-to-build-a-clean-email-list\"><span style=\"font-weight: 400;\">Proper list hygiene <\/span><\/a><span style=\"font-weight: 400;\">requires regular checks of your email list for typos, outdated email addresses, or subscribers who have stopped engaging with your emails altogether.\u00a0<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Opt-In<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">An opt-in is another way of saying that someone has subscribed to your list. The right opt-in practices can prevent list hygiene issues in the first place\u2014like watching for common typos like \u201cgmial\u201d instead of \u201cgmail.\u201d There are two kinds of opt-in practices, single opt-in and double opt-in:<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Single Opt-In<\/span><\/h3>\n<p><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/single-opt-in-vs-double-opt-in-the-verdict-email-permission\"><span style=\"font-weight: 400;\">Single opt-in (SOI)<\/span><\/a><span style=\"font-weight: 400;\"> is when someone subscribes to your mailing list without confirming their email address. Once they type in their email address and click \u201csubscribe,\u201d they\u2019re in. This is a popular acquisition method because it reduces the number of steps subscribers have to take to sign up, but it can make it more difficult to catch typos, bounced email addresses, or spam traps.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Double Opt-In<\/span><\/h3>\n<p><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/single-opt-in-vs-double-opt-in-the-verdict-email-permission\"><span style=\"font-weight: 400;\">Double opt-in <\/span><\/a><span style=\"font-weight: 400;\">(DOI), also known as confirmed opt-in (COI), is when someone subscribes to your mailing list and then must confirm their email address in a two-step process. First, someone types in their email address and clicks \u201csubscribe\u201d on an opt-in form or checkbox. This triggers a confirmation email where the would-be subscriber must click \u201cconfirm\u201d to be added to your email list. While it adds another step, a double opt-in can help with spam complaints and data privacy compliance.\u00a0<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Spam Traps<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Spam traps are commonly used by inbox providers and blocklist providers to catch malicious senders. They are email addresses that were once used by real people, but due to inactivity, have been reclaimed by the ISP to identify spammers. (But, legitimate senders with poor data hygiene or acquisition practices can end up with spam traps on their list). Its only purpose is to identify spammers and senders not utilizing proper list hygiene. This is one of the big deliverability reasons not to purchase an email list.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Opt-Out<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Opt-out is another word for unsubscribing, or when someone requests to no longer receive your emails. (See unsubscribe rate, above.)<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Spam Folder<\/span><\/h3>\n<p><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/how-your-content-could-trigger-the-spam-filter\"><span style=\"font-weight: 400;\">The spam folder,<\/span><\/a><span style=\"font-weight: 400;\"> also known as the \u201cjunk\u201d folder or spam filter, is designed by ISPs to filter out suspicious emails. This includes dangerous or well-known scams, inappropriate or illegal content, or phishing attempts, which compromise the safety and security for the ISP\u2019s users. Spam filtering has become so sophisticated that sometimes email marketers can get caught, too. If you\u2019re consistently <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/how-your-content-could-trigger-the-spam-filter\"><span style=\"font-weight: 400;\">landing in the spam folder<\/span><\/a><span style=\"font-weight: 400;\">, you need to evaluate your email marketing strategy.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Blocklist<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">You don\u2019t want to end up on <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/what-to-do-if-youve-been-blocklisted\"><span style=\"font-weight: 400;\">a blocklist<\/span><\/a><span style=\"font-weight: 400;\"> (formerly known as blacklists). A blocklist is a list of IP addresses or domains that are known to be associated with malicious spammers.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">There are two kinds of blocklists:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>IP blocklisting<\/b><span style=\"font-weight: 400;\"> indicates to anyone who utilizes that blocklist to block the mail originating from that IP address.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">More serious is <\/span><b>domain blocklisting<\/b><span style=\"font-weight: 400;\">. Email marketers can send campaigns from multiple IP addresses, but if your domain appears frequently in emails that hit spam traps, there may be a chance that your entire domain will be blocklisted. This can be even more damaging as the block is not localized to just an IP address, thus affecting you across all your sending platforms.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">On a practical level, individuals can create their own blocklists of senders that are not allowed to email them for whatever reason\u2014a step beyond a spam complaint, if you will.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Allowlist<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Allowlist, previously known as a whitelist, is the opposite of a blocklist. Your subscribers can save you from the spam filter by explicitly telling their mailbox provider that they want to receive your messages. Depending on the inbox provider, they can go into their settings and mark your messages as TINS (This Is Not Spam). This means your server is considered spam-free or is an \u201capproved sender.\u201d<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Email Throttling<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">ISPs can detect a change in email volume, so if you start sending too many emails too quickly, you risk having some (or all) of your emails rejected. Email throttling is when an ISP limits the amount of emails accepted from a sender during a certain time period. When this happens, you\u2019ll see a large number of email bounces. This can also happen if you\u2019re seeing an uptick in spam complaints or unsubscribes\u2014basically, the ISP is wary of your sender reputation and wants to slow it down in case you <\/span><i><span style=\"font-weight: 400;\">are <\/span><\/i><span style=\"font-weight: 400;\">a spammer. (Even if you\u2019re not!)<\/span><\/p>\n<h2><span id=\"email-faq\" style=\"font-weight: 400;\">Email deliverability FAQs<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">Still have email deliverability questions? We\u2019ve compiled some of the questions our customer support team gets most often:<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">What factors affect email deliverability?<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Several factors affect your email deliverability:<\/span><\/p>\n<ul>\n<li><strong>Email volume<\/strong><b>:<\/b><span style=\"font-weight: 400;\"> ISPs look at the number of emails you send, and how frequently you send them, to determine if you\u2019re a spammer.<\/span><\/li>\n<li aria-level=\"1\"><strong>Authentication infrastructure<\/strong><b>: <\/b><span style=\"font-weight: 400;\">You should have your t\u2019s crossed and i\u2019s dotted with your authentication, including SPF, DKIM, and DMARC.\u00a0<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>List quality and engagement<\/b><span style=\"font-weight: 400;\">: How often, and how well, your subscribers engage with your list matters for your deliverability. This is often informed by your list management\u2014whether or not the email addresses on your list want to hear from you in the first place.<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><b>Email content and formatting:<\/b><span style=\"font-weight: 400;\"> Make sure your emails look good in mobile, Dark Mode, and on all email clients before you send. While the impact of your email content is lower than the other factors here, it\u2019s still important as it affects your engagement, which in turn affects your deliverability.\u00a0<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">All of these add up to your sender reputation, which is the score ISPs look at when determining your inbox placement.\u00a0<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">Why are my emails going to the spam folder?<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">After analyzing thousands of emails, we found that <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/spam-filter-tests\"><span style=\"font-weight: 400;\">70% of emails show at least one spam-related issue<\/span><\/a><span style=\"font-weight: 400;\">, so it\u2019s important to look at your email marketing program holistically for deliverability fixes.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">There are a few things you can do if you\u2019re seeing a large percentage of emails going to the spam folder:<\/span><\/p>\n<ul>\n<li><strong>Check your authentication and infrastructure<\/strong><b>:<\/b><span style=\"font-weight: 400;\"> Make sure everything is working correctly with your authentication protocols like SPF, DKIM, and DMARC. Then, double check your infrastructure like your IP reputation.<\/span><\/li>\n<li aria-level=\"1\"><strong>Check your spam complaints<\/strong><b>: <\/b><span style=\"font-weight: 400;\">If someone marks you as spam, you\u2019re going to end up in the spam filter. If you\u2019re seeing a lot of spam complaints, it may be a mismatch between your audience and your content, or your send frequency.<\/span><\/li>\n<li aria-level=\"1\"><strong>Check your unsubscribe process<\/strong><b>: <\/b><span style=\"font-weight: 400;\">Frustrated people trying to unsubscribe from your list may resort to spam complaints. Is it easy for them to unsubscribe? And double check that you\u2019re honoring those unsubscribe requests as soon as possible.<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Here are a few more ways you can <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/why-email-deliverability-matters\"><span style=\"font-weight: 400;\">improve your deliverability.<\/span><\/a><\/p>\n<h3><span style=\"font-weight: 400;\">How do you fix email deliverability?<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">Fixing your email deliverability depends on what caused the problem in the first place\u2014ah, the fickle nature of email!\u2014but there are a few best practices you can follow to address deliverability issues:<\/span><\/p>\n<ul>\n<li><b>Regularly clean your email list:<\/b><span style=\"font-weight: 400;\"> Email list hygiene is not a one-and-done process. One of the first checks you should make (after your infrastructure setup) is your email list. Look for email addresses that have typos, have recently bounced, or no longer engage with your emails.<\/span><\/li>\n<li aria-level=\"1\"><b>Use email personalization to boost engagement: <\/b><span style=\"font-weight: 400;\">High engagement is the secret to better deliverability. Prove to ISPs that your subscribers love getting your emails and you\u2019re more likely to land in the inbox in the future. <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/combining-segmentation-and-personalization\"><span style=\"font-weight: 400;\">Segmentation and personalization<\/span><\/a><span style=\"font-weight: 400;\"> are two techniques to achieve this.<\/span><\/li>\n<li aria-level=\"1\"><b>Switch to double opt-in: <\/b><span style=\"font-weight: 400;\">If you\u2019re consistently struggling with your deliverability, it\u2019s best to prevent issues at acquisition with a double opt-in process. This requires any new email addresses added to your list to be confirmed by a real person, so you know they\u2019re legit (and that they actually want to hear from you.)<\/span><\/li>\n<\/ul>\n<p><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/why-email-deliverability-matters\"><span style=\"font-weight: 400;\">Here are a few more ways<\/span><\/a><span style=\"font-weight: 400;\"> you can fix your deliverability.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">What is a good deliverability rate for email?\u00a0<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">A good email deliverability rate is 95% or higher. (Tbh, we aim for 99%.) That means 95% of the emails you send get delivered <\/span><b>and placed in the inbox or another primary folder.<\/b><\/p>\n<p><span style=\"font-weight: 400;\">Don\u2019t mix up deliverability rate <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/the-difference-between-deliverability-and-delivery-rate\"><span style=\"font-weight: 400;\">with your delivery rate<\/span><\/a><span style=\"font-weight: 400;\">. That measures how many emails you send get delivered, period. While it\u2019s important to have a high delivery rate as well (your emails can\u2019t get placed in the inbox if they\u2019re not delivered), make sure you\u2019re looking at both when evaluating your email marketing performance.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">How often should I clean my email list?<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">You should clean your email list regularly\u2014at least every six months, if not every quarter. It\u2019s a good idea to do a list audit after big email address acquisition events, too, like after a conference or partner marketing swap. Keep an eye on your unsubscribes and bounce rate on a regular basis, which are leading indicators of your overall list hygiene.<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">What role does email testing play in email deliverability?<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">ISPs evaluate a number of factors to determine whether or not your email should be placed in the spam folder or the inbox. If your emails look suspicious\u2014they contain rendering issues, broken or hidden links, or weird formatting\u2014you may get stuck in the spam filter. The best way to prevent this? <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/email-testing\"><span style=\"font-weight: 400;\">Testing your email before every send<\/span><\/a><span style=\"font-weight: 400;\">. (We can help with that.)<\/span><\/p>\n<h3><span style=\"font-weight: 400;\">What tools can help me monitor email deliverability?<\/span><\/h3>\n<p><span style=\"font-weight: 400;\">When we asked email geeks about their deliverability practices, <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/state-of-email-reports\"><span style=\"font-weight: 400;\">22% admitted<\/span><\/a><span style=\"font-weight: 400;\"> to not measuring deliverability at all. This shocked us because there are free tools like <\/span><a rel=\"noopener\" target=\"_blank\" href=\"https:\/\/gmail.com\/postmaster\/\"><span style=\"font-weight: 400;\">Google Postmaster<\/span><\/a><span style=\"font-weight: 400;\"> out there to help you out. You can also use an all-in-one tool like <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/spam-filter-tests\"><span style=\"font-weight: 400;\">Litmus Spam Testing<\/span><\/a><span style=\"font-weight: 400;\">, which looks at your overall deliverability health (like an <a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/blog\/email-deliverability-audit\" target=\"_blank\">email deliverability audit<\/a>) and evaluates specific email campaigns for spam filter flags.<\/span><\/p>\n<h2><span style=\"font-weight: 400;\">Don\u2019t let all these deliverability terms scare you<\/span><\/h2>\n<p><span style=\"font-weight: 400;\">Phew, that was a lot! Deliverability is one of the trickiest parts of email marketing to master. But the good news is, you don\u2019t have to memorize all of these terms right now.<\/span><span style=\"font-weight: 400;\">You can download our handy-dandy cheat sheet\u2014or let Litmus do all the hard work for you. <\/span><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/spam-filter-tests\"><span style=\"font-weight: 400;\">Litmus Spam Testing <\/span><\/a><span style=\"font-weight: 400;\">runs your email marketing campaigns through 20+ filters and provides actionable advice on how to improve your deliverability.<\/span><\/p>\n\n<div class=\"container pt-3 pb-5\">\n\t<div class=\"row blog-cta-blue  p-4\">\n\t\t<div class=\"col-12 mx-auto\">\n\t\t\t<div class=\"row d-flex align-items-center\">\n\t\t\t<div class=\"col-lg-6 col-12\">\n\t\t\t\t<p class=\"bold fs-4\">Deliverability from every angle <\/p>\n\t\t\t\t<p>Get the insights and tools to improve inbox placement, sender reputation, and email performance. <\/p>\n\t\t\t\t<button class=\"button-blue arrow\"><a rel=\"noopener\" href=\"https:\/\/www.litmus.com\/email-deliverability\" class=\"text-white text-decoration-none\">Explore Litmus Deliverability <\/a><\/button>\n\t\t\t<\/div><!--col-6-->\n\t\t\t<div class=\"col-6 d-none d-lg-block\">\n\t\t\t\t<img decoding=\"async\" src=\"https:\/\/www.litmus.com\/wp-content\/uploads\/2024\/12\/blog-cta-12172024.svg\" width=\"208\" height=\"171\" alt=\"\">\n\t\t\t<\/div><!--col-6-->\n\t\t\t<\/div> <!--row-->\n\t\t<\/div><!--col-12-->\n\t<\/div><!--row-->\n<\/div><!--container-->\n\t\n\t\t\n\t\n\t\n\t\n\n<p><em>This article originally published on May 18, 2016. It was updated on December 13, 2024.<\/em><\/p>\n  \t\t\t<\/div>\n  \t\t<\/div>\n  \t<\/div>\n  <\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Knowing some key email deliverability terms that influence whether your email will make it to the inbox as you intend, makes you a more empowered email marketer. Download our email deliverability cheat sheets for a handy reference to keep at your fingertips.<\/p>\n","protected":false},"author":65,"featured_media":106444,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"tags":[45,832,10247,48],"blog_category":[10302],"class_list":["post-5825","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","tag-deliverability","tag-email-service-providers","tag-performance-metrics","tag-spam-filter","blog_category-email-deliverability"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v27.5 (Yoast SEO v27.7) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>Email Deliverability Glossary: Terms You Need to Know | Litmus<\/title>\n<meta name=\"description\" content=\"Master email deliverability with Litmus&#039; comprehensive glossary and FAQs. 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