Email marketing has its own language. ESP, DKIM, CTR, double opt-in, hard bounce, segmentation. If you are a solo founder who just wants to send a newsletter without a marketing degree, half these terms sound like someone dropped a Scrabble board.

You open a deliverability report and see 'Your SPF record is missing, which may affect your DKIM alignment and cause DMARC failures.' This is not helpful. You just wanted to know if people got the email.

This glossary explains 25+ email marketing terms in plain English. No jargon about jargon. Just definitions you can actually use. By the end, you will be able to read a campaign report without opening a second tab to Google every acronym.

The metrics that actually matter

When you send an email, your ESP (email service provider) gives you a report full of numbers. Here is what each one actually means and which ones you should care about.

Open rate: The percentage of people who opened your email. Calculated as unique opens divided by emails delivered. A 20 to 25% open rate is healthy for a small engaged list. Below 15% and your subject lines or sender name might need work. Note: Apple Mail Privacy Protection inflated open rates starting in 2021, so opens from Apple Mail users are less reliable as a signal.

Click-through rate (CTR): The percentage of recipients who clicked at least one link in your email. Calculated as unique clicks divided by emails delivered. A 2 to 5% CTR is typical. Higher means your content matched what people wanted. This is a better engagement signal than open rate because it measures action, not just attention.

Conversion rate: The percentage of recipients who completed your desired action after clicking through (signing up, buying, booking a demo). This is the metric that connects email to revenue. If your open rate and CTR look fine but your conversion rate is zero, the problem is your landing page or your offer, not your email.

Bounce rate: The percentage of emails that could not be delivered. Comes in two flavors. A hard bounce is permanent (invalid address, domain does not exist). A soft bounce is temporary (full inbox, server down). Hard bounces should be removed from your list immediately. Soft bounces get a few retries before removal. Keep your total bounce rate under 2%.

Unsubscribe rate: The percentage of recipients who clicked unsubscribe. Under 0.5% is normal. Higher than 1% means people are getting emails they did not sign up for or your content is not what they expected. Every ESP is legally required to include an unsubscribe link in every marketing email.

Deliverability: Not a metric you see on a dashboard, but the thing that determines whether any of the other numbers matter. Deliverability is your ability to land in the inbox (not spam, not promotions tab, not silently deleted). It depends on sender reputation, authentication (SPF, DKIM, DMARC), list hygiene, and engagement history. More on this in the technical section.

The email types you will actually send

Not all emails are the same. The type of email you send determines its purpose, its format, and the rules that apply to it.

Newsletter: A regular email sent to your entire list (or a segment) with updates, content, or offers. This is the email type most solo founders start with. Think of it as your weekly check-in with people who said they want to hear from you. Examples: a product update, a roundup of your recent blog posts, a personal story that ties back to your product.

Drip campaign: A series of pre-written emails sent automatically based on timing or user behavior. Also called an email sequence or automation. Examples: a 5-email welcome series when someone signs up, a re-engagement sequence when someone goes quiet, a product onboarding flow. You write it once and your ESP sends it on schedule. This is where email marketing earns its keep.

Transactional email: An automated email triggered by a specific user action. Password resets, order confirmations, shipping notifications, account verification emails. These are not marketing emails. They do not require an unsubscribe link (though many ESPs add one anyway). They have the highest open rates of any email type because people actually need the information inside.

Broadcast (batch and blast): A single email sent to your entire list at once. This is the simplest email type. You write one message, hit send, and everyone gets the same thing. It is fast and it works for announcements or time-sensitive offers. The downside: no personalization, and sending too many broadcasts to people who have not engaged in months will tank your deliverability.

Autoresponder: A single automated email triggered by an action (signup, purchase, form submission). The simplest form of automation. You set it once, and every new subscriber gets it automatically. A welcome email is the classic example. Most solo founders should set up at least one autoresponder: a thank you email that goes out the moment someone joins your list.

The technical stuff (explained in plain english)

This is the section most glossaries turn into alphabet soup. We will keep it short and practical.

ESP (email service provider): The platform you use to build, send, and track emails. Mailchimp, ConvertKit, Klaviyo, Brevo, and MailerLite are all ESPs. Most include list management, templates, automation, and analytics. For a solo founder, the right ESP is the one that charges based on your actual list size and does not lock features behind enterprise pricing tiers. Tools like ad-vertly.ai exist for founders who want the marketing done for them without learning any of this jargon.

SPF (sender policy framework): A DNS record that tells the world which servers are allowed to send email from your domain. Think of it as a bouncer with a guest list. If a server not on the list tries to send email pretending to be you, SPF says no. Your ESP will give you the exact record to add to your domain. Takes 5 minutes. Prevents spammers from spoofing your domain.

DKIM (DomainKeys Identified Mail): A digital signature attached to every email you send. The receiving server checks the signature against a public key stored in your DNS records. If they match, the email has not been tampered with. Together with SPF, DKIM proves your emails are genuinely from you. Most ESPs handle the setup. You add a DNS record they provide and you are done.

DMARC (Domain-based Message Authentication, Reporting, and Conformance): The policy layer on top of SPF and DKIM. DMARC tells receiving servers what to do when an email fails authentication: do nothing, quarantine it (send to spam), or reject it outright. As of 2024, Google and Yahoo require DMARC for anyone sending more than 5,000 emails per day. Even below that threshold, setting it up is free and takes 10 minutes. Your ESP has a guide.

IP warming: If you switch ESPs or start sending from a new dedicated IP, you cannot send 10,000 emails on day one. ISPs will see a sudden spike from an unknown sender and block you. IP warming means starting small (50 emails on day one) and increasing volume gradually over 2 to 4 weeks. Most shared-IP ESPs handle this for you. Only relevant if you are on a dedicated IP plan.

Sender reputation: A score (often called Sender Score) that ISPs assign to your sending domain and IP based on engagement, bounce rates, spam complaints, and list hygiene. Think of it as a credit score for email. A high score means inbox. A low score means spam folder. You build it by sending to people who open and click, and you destroy it by buying lists or ignoring bounce rates.

Compliance terms you cannot ignore

Email marketing is regulated. Ignorance is not a legal defense. Here are the terms that keep you out of trouble.

CAN-SPAM Act: The U.S. law governing commercial email (since 2003). It requires three things: a visible unsubscribe link in every email, accurate sender information (real name, real reply-to address), and a physical mailing address in the footer. Violations can cost up to $51,744 per email. Yes, per email. Most ESPs enforce CAN-SPAM compliance by default, but you are still legally responsible.

GDPR (General Data Protection Regulation): The EU privacy law that applies to anyone collecting data from EU residents (including email addresses). GDPR requires explicit consent before adding someone to your list. Pre-checked boxes do not count. Users must take a clear affirmative action. It also gives people the right to request deletion of their data. Even if you are based outside the EU, if you have EU subscribers, GDPR applies.

Opt-in (single vs. double): Single opt-in means someone enters their email and is immediately subscribed. Double opt-in adds a confirmation step: they get an email with a link they must click to confirm. Double opt-in produces smaller lists but higher engagement and fewer spam complaints. For a solo founder building a reputation from scratch, double opt-in is worth the smaller initial numbers.

Unsubscribe link: A link in every marketing email that lets recipients opt out. Required by law in nearly every jurisdiction. Must be functional for at least 30 days after sending. Most ESPs add this automatically. Do not remove it. Do not bury it in 6pt font at the bottom of a 2,000-word email. Make it visible. People who want to leave will leave. The ones who stay are the ones who matter.

List management terms

Your email list is not just a CSV file. How you manage it determines whether your emails land in inboxes or spam folders.

Segmentation: Dividing your list into groups based on behavior, demographics, or preferences. Segmented campaigns get 14% higher open rates and 100% higher click rates than non-segmented ones (Mailchimp data). Simple segments for a solo founder: new subscribers (first 30 days), engaged subscribers (opened in the last 90 days), inactive subscribers (no opens in 90+ days). Send different content to each.

List hygiene: The practice of regularly removing invalid, inactive, and disengaged addresses from your list. It sounds counterintuitive (why make your list smaller?), but sending to people who never open hurts your sender reputation. Most ESPs charge based on subscriber count, so you are also paying to email people who ignore you. Clean your list quarterly. Remove hard bounces weekly.

Churn rate: The rate at which subscribers leave your list (unsubscribe, bounce, or mark as spam). A churn rate of 2 to 5% per month is normal for a healthy list. If your churn rate spikes after a particular campaign, the content or frequency was off. Track this alongside your list growth. If you add 100 subscribers and lose 90, your list is not growing. It is treading water.

Suppression list: A list of email addresses your ESP automatically excludes from campaigns. It includes people who unsubscribed, hard bounced, or marked you as spam. You never see this list or manage it manually. Your ESP handles it. The important thing: if you switch ESPs, export your suppression list and import it into the new platform. Otherwise you will email people who already told you to stop.

Graymail: Emails that are not spam but that the recipient no longer engages with. They opted in at some point. They just stopped opening. Graymail is the silent list killer. A list where 40% of subscribers are graymail looks bigger than it actually is. The fix: send a re-engagement campaign after 90 days of inactivity. If they still do not open, remove them. A smaller engaged list outperforms a large dead one every time.

How to stop googling and start sending

You do not need to memorize every term in this glossary. Bookmark it. Come back when someone says 'your DMARC policy is set to p=none' and you need to know whether that matters (it does not, p=none means DMARC is monitoring but not enforcing, which is fine for most solo founders).

The minimum viable email setup for a solo founder is: pick an ESP, set up SPF and DKIM (your ESP will walk you through it), create a double opt-in signup form, write a welcome autoresponder, and send a newsletter when you have something worth saying. That is it. You can add drip campaigns, segmentation, and A/B testing later when you have enough subscribers for the data to be meaningful.

If you are looking for an ESP that does not punish small lists with enterprise pricing, we have written about Klaviyo alternatives for solo founders and Mailchimp alternatives for solo founders. Both cover tools that fit a one-person budget.

And if you are tired of learning email marketing terminology altogether, ad-vertly.ai is a full-stack marketing agent built for solo founders. It handles blog posts, SEO, email campaigns, and paid ads without you touching a dashboard or memorizing a glossary.