glossary
email marketing, minus the jargon.
29 terms that come up when you work on email for an online shop, each explained in a sentence or two. Where a number appears, we name its source.
Grouped by where you run into the word: building flows, reading reports, looking after the list, or keeping mail out of the spam folder.
last checked 22 September 2026flows and campaigns
- Retention marketing
- Marketing aimed at getting existing customers to buy again, rather than finding new ones. Email is its main channel because it reaches people who already agreed to hear from you, without paying for each contact.
- Flow
- An automated sequence of emails that starts when a customer does something, such as signing up, leaving a checkout or placing an order, or when a date comes around. Once live, a flow runs on its own for every person who triggers it. The five flows most shops need.
- Campaign
- A one-off email sent to the whole list or a segment at a time you choose: a newsletter, a launch, a sale. In Klaviyo's 2026 benchmarks, 0.16 percent of campaign recipients placed an order on average, against 2.11 percent for flows.
- Welcome series
- The flow that starts when someone subscribes. It introduces the brand and makes the first purchase easy. It reaches people at the moment they chose to hear from you, so it gets more attention than almost anything else you send.
- Abandoned cart flow
- Emails to shoppers who put something in the cart or started checkout and left without buying. Most setups trigger on the started checkout, because that is where the shop first learns the email address.
- Browse abandonment flow
- A reminder to a known subscriber who looked at products without adding anything to the cart. It only works for visitors the email platform recognises, for example after they clicked an email.
- Post-purchase flow
- Everything sent after an order: confirmation and shipping updates first, then how to use the product, then a review request or a next product. Done well, it answers "where is my order?" before that question turns into a support ticket. Examples.
- Win-back flow
- Emails to customers who haven't ordered for longer than your usual gap between purchases. If a discount appears anywhere in your flows, this is where it belongs, because the alternative is losing the customer.
- Replenishment flow
- A reminder timed to when a product typically runs out, such as a month's supply of coffee or supplements. It only makes sense for consumables.
- Sunset flow
- A last attempt to re-engage subscribers who haven't opened or clicked in months. The ones who stay silent stop receiving mail. This protects deliverability, because mailbox providers read ignored mail as a bad sign.
metrics
- Open rate
- The share of delivered emails that were opened. Klaviyo's 2026 average for ecommerce campaigns is 31 percent. Since Apple Mail Privacy Protection, the number is inflated and no longer a reliable signal on its own.
- Click rate
- The share of delivered emails in which someone clicked at least one link. In Klaviyo's 2026 data the average is 1.69 percent for campaigns and 5.58 percent for flows. It is more trustworthy than open rate, because a click needs a person.
- Click-to-open rate (CTOR)
- Clicks divided by opens. It is meant to show how well the content worked for the people who opened, but inflated opens drag it down, so compare it only against your own history.
- Placed order rate
- The share of recipients who placed an order that the platform attributes to the email. Of the numbers most email platforms report, it is the one closest to money.
- Revenue per recipient (RPR)
- Attributed revenue divided by the number of recipients. It puts a small flow and a big campaign on the same scale, so you can compare them.
- Attribution
- The rule that decides which channel gets credit for an order. Email platforms usually credit the last email clicked within a set number of days. That flatters email, because some of those customers would have bought anyway.
- Repeat purchase rate
- The share of customers who ordered more than once in a given period. There is no trustworthy industry average: the often quoted 27 to 30 percent has no traceable source, as our statistics page shows. Compare against your own previous quarter.
- Average order value (AOV)
- Revenue divided by the number of orders. Bundles, a free shipping threshold and fitting add-ons in the emails after a purchase are the usual ways to raise it.
- Customer lifetime value (CLV)
- The revenue, or better the margin, a customer brings over the whole relationship. It sets how much you can afford to spend on winning a customer in the first place.
- Churn
- Customers who stop buying. Outside subscriptions nobody cancels, so a shop has to define it itself, usually as no order for clearly longer than the typical gap between purchases.
list and data
- Segment
- A subgroup of your list defined by behaviour or properties, such as "ordered twice" or "no order in 90 days". In most platforms, segments update themselves as customers act.
- RFM segmentation
- Grouping customers by recency, frequency and monetary value: how recently they bought, how often, and how much. It separates your best customers from the ones drifting away.
- Double opt-in
- The subscriber confirms their address by clicking a link in a confirmation email before they are added to the list. In Germany it is the usual way to prove consent to email marketing, and proving it is the sender's job.
- Zero-party data
- Information customers give you on purpose, such as their skin type in a quiz or favourite categories in a signup form. You don't have to guess it from clicks.
deliverability
- Deliverability
- Whether your email reaches the inbox rather than the spam folder or nowhere at all. It depends on authentication, on the complaint rate, and on how many of your recipients actually engage.
- SPF, DKIM and DMARC
- Three DNS records that prove mail really comes from your domain. SPF lists the servers allowed to send for it, DKIM signs each message, and DMARC tells mailbox providers what to do when those checks fail. Since 1 February 2024, Google requires all three from anyone sending more than 5,000 messages a day to Gmail addresses.
- Spam complaint rate
- The share of recipients who mark an email as spam. Google requires senders to stay below 0.3 percent and recommends staying under 0.1 percent.
- Bounce
- An email that could not be delivered. A hard bounce is permanent, such as an address that doesn't exist, and that address should leave the list at once. A soft bounce is temporary, such as a full inbox.
- Apple Mail Privacy Protection
- A feature Apple introduced with iOS 15 in September 2021. Apple Mail loads images, including the tracking pixel, through its own servers in advance, so an email can count as opened without anyone reading it.
questions rather than terms?
The FAQ covers cost, timing and how to judge an agency. The numbers behind these definitions, with sources, are on the statistics page.
too many terms, not enough time?
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