> ## Documentation Index > Fetch the complete documentation index at: https://docs.letterbucket.com/llms.txt > Use this file to discover all available pages before exploring further. # Glossary > Find here all the terminology we use ## A/B Testing A way to test which version of your [newsletter](#newsletter) performs better. You send version A to one group and version B to another (for example, two different subject lines). The version with more [opens](#open-rate) or [clicks](#click-rate) wins, and you can use it for the rest of your [audience](#audience). This helps you make decisions based on real data instead of guessing. ## Analytics Numbers and charts that show how your emails perform. Typical metrics include [open rate](#open-rate), [click rate](#click-rate), [unsubscribes](#opt-out), and [bounce rate](#bounce). Analytics help you understand what your audience likes, what they ignore, and how to improve over time. ## Audience The group of people who subscribed to your [newsletter](#newsletter). Your audience is your community, whether it’s 50 readers or 50,000. It's common to talk about audience and [subscribers](#subscribers) indistinctly. ## Authentication The process of proving that an email is really sent by you and not by a spammer pretending to be you. It’s like putting your signature and stamp of approval on every message. The main tools for this are [SPF](#spf), [DKIM](#dkim), and [DMARC](#dmarc). LetterBucket handles this automatically for you. ## Blacklist A list used by [email clients](#email-client) and providers to block unwanted senders. If your [domain](#custom-domain) or [IP address](#ip-address) ends up on a blacklist, your emails may go straight to [spam](#spam) or not be delivered at all. Good practices help you avoid this. ## Bounce When an email can’t be delivered to a subscriber’s [inbox](#inbox). * **Hard bounce:** permanent problem, like an address that doesn’t exist. You must keep your [email list](#email-list) clean to avoid sending to these addresses because it sends negative signals to [email clients](#email-client). * **Soft bounce:** temporary problem, like a full inbox or a server issue. If you repeatedly try to send to an address and it keeps soft bouncing, you should remove it from your list. Bounces affect your [domain reputation](#domain-reputation), so cleaning your list regularly is important. **Ideal range:** Bounce rate should stay **below 2%**. Higher rates mean your list needs cleaning. ## Campaign A single [newsletter](#newsletter) (or series of emails) you send to your [audience](#audience). For example, your weekly newsletter is a campaign, as is a special announcement. ## CAN-SPAM A US law that sets the rules for email marketing. It requires things like clear [unsubscribe links](#unsubscribe-link) and forbids deceptive subject lines. Even if you’re not in the US, respecting these rules improves trust with your audience. ## Click Rate The percentage of readers who clicked a link in your [newsletter](#newsletter). If 100 people open your email and 10 click, your click rate is 10%. **Ideal range:** **2–5%** is common, **5–10%+** is excellent (depends on industry and audience engagement). ## CTR (Click-Through Rate) Another name for [click rate](#click-rate). Same concept. ## CSV File A simple file format that looks like a spreadsheet. It’s commonly used to upload or download [subscriber](#subscriber) lists between platforms. It means “comma-separated values,” which is a way of formatting data. ## CTA (Call to Action) The action you want your reader to take. Examples: “Read more,” “Subscribe,” or “Buy now.” A clear CTA helps readers know what to do next. ## Custom Domain Your [own branded web address](https://docs.letterbucket.com/custom-domain/set-custom-domain) for your [newsletter](#newsletter), like **yourname.com**, instead of a generic link. This makes you look more professional and improves [deliverability](#deliverability). ## Deliverability How likely your [newsletter](#newsletter) is to land in the [inbox](#inbox) instead of the [spam](#spam) folder. Good content, a clean [email list](#email-list), and proper [authentication](#authentication) all boost deliverability. ## Delivery Rate The percentage of emails that were successfully delivered (didn’t [bounce](#bounce)). A high delivery rate shows your list is healthy. **Ideal range:** Aim for **above 98%**. Anything lower means you may have list quality or [deliverability issues](https://docs.letterbucket.com/deliverability). ## DKIM (DomainKeys Identified Mail) A system that adds a digital signature to your emails. It’s like sealing an envelope so the receiver knows it hasn’t been tampered with. It proves that the message really came from your [domain](#custom-domain). LetterBucket handles this automatically, so you don’t need to worry about it. ## DMARC (Domain-based Message Authentication, Reporting & Conformance) A rule you set for your [domain](#custom-domain) that tells [inboxes](#inbox) what to do if an email fails [SPF](#spf) or [DKIM](#dkim). For example: accept it, send it to [spam](#spam), or block it. DMARC also gives you reports about who is trying to send emails using your domain. We also handle this for you. ## DNS (Domain Name System) The “phonebook” of the internet. DNS translates easy-to-remember names (like letterbucket.com) into the numerical [IP addresses](#ip-address) computers use to find each other. In the context of email, DNS is also where you set up important records ([SPF](#spf), [DKIM](#dkim), [DMARC](#dmarc), [MX](#mx-record)) that prove you’re a legitimate sender and tell [inboxes](#inbox) how to handle your messages. If DNS is misconfigured, your emails may land in [spam](#spam) or not get delivered at all. This is configured automatically by us. ## Domain Reputation Your sending reputation in the eyes of [email clients](#email-client) like Gmail or Outlook. If you send wanted, engaging [newsletters](#newsletter), your reputation improves. If people mark your emails as [spam](#spam), it goes down. This is the most critical aspect of your [deliverability](#deliverability). ## Double Opt-In A process where [subscribers](#subscriber) confirm their email address after signing up. They get a confirmation email and must click a link. This ensures that only people who truly want your [newsletter](#newsletter) join your list. ## Email Client The app or service people use to read their [emails](#newsletter). Popular email clients include Gmail, Outlook, Yahoo Mail, and Apple Mail. Each client has its own way of displaying emails, which means your [newsletter](#newsletter) might look slightly different depending on where it’s opened. Some clients clip long emails, block images by default, or show the [promotions tab](#promotions-tab) separately from the [inbox](#inbox). Understanding how email clients behave helps you design messages that look good everywhere. ## Email List The collection of [subscribers](#subscriber) who signed up to receive your [newsletter](#newsletter). Your email list is one of your most valuable assets as a creator, because it’s an audience you own, not borrowed from social media platforms. Healthy email lists grow through [opt-ins](#opt-in), shrink a little through [opt-outs](#opt-out), and perform best when you practice good [list hygiene](#list-hygiene). A clean, engaged list keeps your [deliverability](#deliverability) high and ensures your content reaches readers who actually want it. ## ESP (Email Service Provider) A company or platform that helps you send [emails](#newsletter) to large groups of [subscribers](#subscriber) without getting blocked by [spam filters](#spam-filter). ESPs handle the technical side of [deliverability](#deliverability), like [authentication](#authentication), [IP addresses](#ip-address), and [DNS](#dns) settings, so you can focus on writing. LetterBucket is an ESP made for newsletters. Other tools can send newsletters too, but because they’re built for broader email marketing they can’t fine-tune things like newsletter design and deliverability the way we do. ## Footer The section at the bottom of a [newsletter](#newsletter). It usually includes your [unsubscribe link](#unsubscribe-link), legal info, or contact details. ## From Address The email address your readers see in their [inbox](#inbox) when you send a [newsletter](#newsletter) (like [hello@yourdomain.com](mailto:hello@yourdomain.com)). ## GDPR (General Data Protection Regulation) A European law that protects personal data. It requires transparency, clear consent, and gives [subscribers](#subscriber) rights over their data. Even if you’re outside Europe, GDPR standards are a good trust practice. ## Header The hidden technical part of an email that carries metadata like who sent it, where it came from, and [authentication](#authentication) results. Most readers never see this, but [inboxes](#inbox) use it to decide if your message is legitimate. ## HTML Email An email built with HTML code, which allows for design, colors, images, and formatting. Most newsletters are HTML emails. Even if you just write [plain text](#plain-text-email), it’s still built in HTML under the hood. ## Inbox The place where received emails show up in your [email client](#email-client). When we talk about “landing in the inbox,” it means your email successfully avoided the [spam](#spam) or [promotions folder](#promotions-tab) and arrived where the reader is most likely to see it. For creators, the inbox is where you want every [newsletter](#newsletter) to land. ## IP Address A unique number that identifies the server that sent your emails. It’s like your return address on a letter. ## Landing Page A simple webpage with one clear goal, like collecting sign-ups for your [newsletter](#newsletter). ## List Hygiene The practice of keeping your [email list](#email-list) clean by removing invalid, inactive, or unengaged [subscribers](#subscriber). This improves [deliverability](#deliverability). ## MX Record (Mail Exchange Record) A special [DNS](#dns) record that tells the internet where to deliver emails for your [domain](#custom-domain). LetterBucket handles this for you. ## Newsletter A recurring email you send to your [audience](#audience). It usually includes updates, articles, or insights. It’s the main product most creators publish with LetterBucket. ## Open Rate The percentage of [subscribers](#subscriber) who opened your [newsletter](#newsletter). This is tracked using a [tracking pixel](#tracking-pixel). **Ideal range:** * **20–30%** is typical. * **30–40%+** is very good. * Below **15%** may signal [subject line](#preview-text) issues, [spam](#spam) folder placement, or list fatigue. ## Opt-In When someone gives you permission to receive emails. This is the legal and ethical way to build your [email list](#email-list). ## Opt-Out When someone unsubscribes from your [newsletter](#newsletter). Every marketing email must include this option. ## Personalization Adding a personal touch to your emails, like using the reader’s name or tailoring content to their interests. ## Plain Text Email An email with only text and no design or images. Simple and often more personal. ## Preview Text The short snippet of text that appears next to the subject line in the [inbox](#inbox). It gives readers a sneak peek of what’s inside. ## Promotions Tab A special folder in Gmail where marketing and bulk [emails](#newsletter) often land instead of the main [inbox](#inbox). The Promotions tab isn’t the same as the [spam folder](#spam), your [subscribers](#subscriber) can still see your messages, but they may check this tab less often. **Landing in Promotions is common for newsletters**, especially if they contain lots of links, images, or promotional language. It doesn’t harm your [deliverability](#deliverability), but you’ll usually get lower [open rates](#open-rate) compared to landing in the main inbox. That said, in practice there’s a big difference: emails in Promotions usually get lower [open rates](#open-rate) because many readers don’t check this tab as often as their main inbox. ## Reply-To Address The email address where replies are sent if someone clicks “Reply” to your [newsletter](#newsletter). You can set this to your preferred inbox. ## Segmentation Dividing your [email list](#email-list) into groups based on criteria like location, behavior, or interests. This allows you to send more relevant [campaigns](#campaign). ## Sender Name The name that appears in the [inbox](#inbox) as the sender, like “John Doe”. Your sender name is often the very first thing a [subscriber](#subscriber) notices, even before the [subject line](#preview-text). It plays a huge role in whether someone decides to open your [newsletter](#newsletter). Many creators use their personal name (“Sarah Johnson”) or a mix of personal and brand (“Sarah from TechNotes”) to make the email feel more trustworthy and human. Using just a brand name can sometimes feel cold or impersonal, while using only a first name may confuse readers if they don’t immediately recognize you. **Best practice:** Keep your sender name consistent across campaigns. Changing it often can confuse [spam filters](#spam-filter) and your audience. A clear, recognizable sender name builds trust and improves [open rates](#open-rate). ## Single Opt-In When someone subscribes to your [email list](#email-list) and is added immediately, without a confirmation step. This is not a good practice, so most providers only allow [double opt-in](#double-opt-in). ## SMTP (Simple Mail Transfer Protocol) The system that email servers use to send messages to each other. It’s the postal service of the internet. ## SPAM Unwanted or irrelevant emails, often sent in bulk without permission. Being labeled as spam hurts your [domain reputation](#domain-reputation). ## Spam Complaint Rate The percentage of [subscribers](#subscriber) who mark your [newsletter](#newsletter) as [spam](#spam) using the “Report Spam” button in their [email client](#email-client). This is one of the most important signals that [spam filters](#spam-filter) use to decide whether your future emails land in the [inbox](#inbox) or get blocked. Even a few complaints can hurt your [domain reputation](#domain-reputation). **Ideal range:** Keep spam complaints **below 0.1%** (that’s fewer than 1 complaint per 1,000 emails). Anything higher is a red flag and can damage your [deliverability](#deliverability). ## Spam Filter A system used by [email clients](#email-client) like Gmail or Outlook to automatically decide whether an [email](#newsletter) should go to the [inbox](#inbox) or to the [spam](#spam) folder. Spam filters look at many signals, including your [domain reputation](#domain-reputation), [authentication](#authentication) (SPF, DKIM, DMARC), how often people open or click, and whether readers mark your messages as spam. For creators, the goal is to pass spam filters and land in the inbox so your [subscribers](#subscriber) actually see your content. ## SPF (Sender Policy Framework) A [DNS](#dns) record that says which servers are allowed to send emails for your [domain](#custom-domain). It helps prevent spammers from faking your address. ## Subscriber A person who has signed up to receive your [newsletter](#newsletter). We also call subscribers audience. ## Suppression List A list of email addresses you don’t send to. This usually includes [opt-outs](#opt-out), complaints, or addresses that [bounced](#bounce). ## Template A pre-designed layout for your [newsletter](#newsletter). Templates make sending consistent [campaigns](#campaign) faster and helps you create a recognizable brand. ## Tracking Pixel A tiny invisible image added to your [newsletter](#newsletter) that loads when someone opens it. This is how [open rates](#open-rate) are measured. ## Transactional Email An automatic, one-to-one email triggered by an action (like a password reset or order confirmation). Unlike [campaigns](#campaign), these are functional, not promotional. ## Unsubscribe Link A link that allows [subscribers](#subscriber) to stop receiving your [newsletter](#newsletter). Required by law and good practice. ## Whitelist A “safe sender” list. If someone whitelists you, your emails are less likely to go to [spam](#spam).