Email subject lines for online stores, by flow
Email subject lines for an online store, flow by flow. Welcome, abandoned cart, checkout, post-purchase, winback and Black Friday, with preview text.
Manuel Sierra
Founder, One Mail Studio
Published · 9 min read
Design and copyIn this article · 12 sections
- The flow tells you what the subject line has to do
- Subject line and preview text are one unit
- Welcome flow subject lines
- Abandoned cart subject lines
- Abandoned checkout subject lines
- Post-purchase subject lines
- Winback subject lines
- Campaign subject lines need three options, not one
- Black Friday subject lines without shouting
- What never goes in a subject line
- How to test subject lines in Klaviyo
- Sources
A good email subject line for an online store depends on where the reader is: someone who just signed up, someone who left a cart and someone who bought last week need different subject lines. Write each one for that moment, keep it under 60 characters, and pair it with preview text that adds something instead of repeating it. Below are the subject lines we would write for each flow, with the reason each one works.
Most lists of subject lines are written for cold outreach or office email. A store sends flows triggered by what a customer did, plus campaigns, so this guide goes flow by flow.
The flow tells you what the subject line has to do
Before writing a word, ask what the reader already knows. That decides the job of the subject line.
| Flow | What the reader knows | Job of the subject line |
|---|---|---|
| Welcome | Your name, not much else | Keep the promise of the sign-up form |
| Abandoned cart | The product they liked | Remind them, without pressure |
| Abandoned checkout | They nearly paid | Offer help, assume something went wrong |
| Post-purchase | They trust you with money | Make the wait and the first use easier |
| Winback | They have not opened you in months | Give them a real reason to look again |
| Campaign | Whatever your last emails taught them | Create a reason to open today |
In flows, the context does half the work, so a plain subject line that names what the reader did beats a clever one.
Subject line and preview text are one unit
In the inbox the reader sees three things together: the sender name, the subject line and the preview text. Klaviyo's help centre describes preview text as one of the first things recipients see, shown after the subject line. If you leave it empty, inboxes pull the first text of the email, which can be your navigation bar or an image's alt text.
Our rules for the pair:
- The subject line opens, the preview text adds. Never the same idea twice. If the subject asks a question, the preview sharpens it; it does not answer it.
- Under 60 characters for the subject line, counted, not guessed. Phones cut it off beyond that.
- The most important words go first in the preview. Klaviyo's own table shows Gmail on iOS displaying as few as 34 characters of preview text, while Outlook.com shows up to 236.
- One idea per pair. If you need two, you need two emails.
Welcome flow subject lines
The first email arrives seconds after the sign-up. Whatever the form promised, the subject line delivers it. Then the series introduces the brand.
| Subject line | Preview text | Why it works |
|---|---|---|
| Your welcome code is inside | Valid for 7 days, on anything in the store | Delivers the promise, the preview sets the limit |
| Why we started making these | The short version, with the workshop photos | Opens a story the email closes |
| The three products people start with | And how to choose between them | Answers the newcomer's first question |
The welcome email that only says "Welcome to the family" wastes the moment with the most attention. Name what they get. For the full sequence with timing, see our welcome flow resource.
Abandoned cart subject lines
The reader added a product and left. They know exactly what it was, so the subject line can be short and plain.
| Subject line | Preview text | Why it works |
|---|---|---|
| You left something in your cart | We saved it for you, same size and color | Direct, and the preview removes friction |
| Still thinking it over? | Here is what other customers asked first | Accepts the doubt instead of fighting it |
| Free returns, in case that was the worry | 30 days to change your mind | Answers the most common objection |
No "Last chance!" in the first email. Nothing is about to run out, and the reader knows it. Timing, discounts and the filter that stops reminders after a purchase are in our abandoned cart email guide.
Abandoned checkout subject lines
Someone who reached checkout had already decided. Assume a problem and offer help.
| Subject line | Preview text | Why it works |
|---|---|---|
| Did something go wrong at checkout? | Your order is saved, one click to finish it | A real question, with the way back in the preview |
| Your order is one step away | Shipping and delivery times, all in one place | Plain status, plus the usual missing detail |
| Can we help with your order? | Reply to this email and a person will answer | Offers a human, not a discount |
Post-purchase subject lines
After a purchase the reader wants information, not persuasion. These subject lines can be almost transactional, and that is a good thing.
| Subject line | Preview text | Why it works |
|---|---|---|
| Your order is on its way | Tracking inside, and what to expect when it arrives | Tells them what they were waiting for |
| How to get the most out of your first one | Two minutes, with the mistakes to avoid | Help that cuts returns and builds trust |
| How is it going so far? | Your review helps the next customer choose | Asks at the right moment, after use |
Keep the selling for later in the flow.
Winback subject lines
Winback goes to people who stopped opening or buying. The worst subject line here is one that looks like every email they already ignored.
| Subject line | Preview text | Why it works |
|---|---|---|
| It has been a while | Here is what changed since your last order | Honest, and the preview gives a reason |
| We changed the thing you asked about | New sizes, and a better return window | Only works if it is true, and then it works well |
| Should we keep writing to you? | One click to stay, or to stop hearing from us | Respects the reader and cleans the list |
That last one matters for your list health. Someone who will never open again is better unsubscribed than marking you as spam. If you want to see how your domain is set up for that, run it through our email deliverability checker.
Campaign subject lines need three options, not one
Campaigns have no trigger to lean on, so the subject line works harder. For every campaign we write three, each in a different register, and mark one as recommended:
- Curiosity: opens a loop the email closes. "The one we almost did not launch."
- Direct benefit: says what the reader gets. "Free shipping on everything this weekend."
- Proof: leans on something real. "Sold out in March, back today."
Three variations of the same idea are not three options, they are one. And do not repeat the subject format or the emoji you used in the previous send. Emoji are a brand decision: some brands use them in every subject line, others never. Pick one and keep it.
Black Friday subject lines without shouting
Black Friday 2026 falls on Friday, November 27. That week every inbox fills with capital letters and countdowns, and that is exactly why a calm subject line stands out.
| Subject line | Preview text | Why it works |
|---|---|---|
| Early access for you, from today | The list gets in 24 hours before everyone else | Rewards the waitlist, no shouting |
| Our Black Friday, in one line | 20% on the full collection until Monday | The news is the news, said plainly |
| The sale ends tonight at midnight | The sizes still left, in one email | A real deadline with useful detail |
Urgency is fine when it is true: the sale really ends, the stock really is limited. Invented urgency costs you trust for the rest of the year. The day-by-day plan for that week is in our Black Friday email plan.
What never goes in a subject line
These are about trust, and Google and the US Federal Trade Commission put some of them in writing.
- Nothing that misrepresents the email. The FTC's CAN-SPAM guide says the subject line must accurately reflect the content of the message. Google's sender guidelines say subject lines should accurately represent the message content and not be misleading.
- No fake "Re:" or "Fwd:". Google's guidelines say not to start a subject line with them unless the message really is a reply or a forward.
- No all capitals and no promise the email does not keep. The reader notices once, and remembers.
- No describing the email. "October newsletter" tells the reader nothing to open for.
How to test subject lines in Klaviyo
Klaviyo lets you A/B test subject lines in both campaigns and flows. In a campaign, it sends a test to part of the list and the rest receive the winning variation. In a flow, the variations can change the subject line, preview text, sender name and sender email, and Klaviyo can end the test on its own once the winner is statistically significant.
Choose click rate as the winning metric, not open rate. Klaviyo recommends it too, because Apple Mail Privacy Protection can inflate open rates. A subject line that gets opens but no clicks promised something the email did not deliver.
If you would rather have someone write and test them with you, book a call.
Sources
Checked on October 5, 2026.
- Subject lines
- Copywriting
- Flows
- Klaviyo
Common questions
What is a good email subject line?
One that tells the reader why to open this email now, in under 60 characters, and matches what the email actually contains. For a store, the best subject line depends on the flow: plain and specific in automated flows, with a clear reason to open in campaigns.
What is an example of a good email subject line for a store?
For an abandoned checkout, "Did something go wrong at checkout?" with the preview text "Your order is saved, one click to finish it". It names what the reader did, offers help and gives the way back in the preview.
What are the best practices for email subject lines in 2026?
Keep them under 60 characters, write preview text that adds to the subject instead of repeating it, and never mislead: Google and the FTC both ask that subject lines reflect the content. Test with click rate as the winning metric, since privacy features inflate open rates.
How do you write an eye-catching subject line without clickbait?
Use something true: a concrete detail, a question the reader is already asking, or a real deadline. Curiosity works when the email closes the loop it opened. Capitals, fake urgency and fake "Re:" get attention once and cost trust after that.
What is preview text and does it matter?
It is the line shown after the subject line in the inbox. It matters because if you leave it empty, the inbox fills it with the first text of the email, often the navigation bar. Treat it as the second line of the subject.
Keep reading
All articles
Abandoned cart emails, the complete guide for Klaviyo and Shopify
How to set up abandoned cart and checkout emails that recover sales, when to send each one, when to add a discount and how to avoid double sends with Shopify.
6 min read
How to plan Black Friday emails without burning your list
What to set up in October, what to send each day of Black Friday week and who should get it, with the 2026 dates and the plan we use with clients.
6 min read
Klaviyo vs Mailchimp for ecommerce, with the real prices
Klaviyo and Mailchimp compared on October 2026 list prices, which contacts each one bills you for, and when paying more for Klaviyo makes sense.
6 min read
Want us to look at your account?
We look at your whole account in a 30-minute call and tell you what we would do first. No strings attached.
Book your free audit