Email marketing should be one of the most profitable channels for any ecommerce brand. The data consistently shows that well-executed email generates £30-40 for every £1 spent — an ROI that no other marketing channel can match at scale. Yet most ecommerce brands we work with are leaving 50-70% of their email revenue potential untapped because of mistakes that are entirely avoidable.
These are not obscure, advanced mistakes. They are fundamental errors in strategy, execution, and maintenance that we see repeated across brands of all sizes. If you are making even three or four of these, fixing them will have a material impact on your revenue within weeks, not months.
Why email mistakes cost more than you think
Email marketing mistakes do not just reduce revenue — they compound over time. A poorly configured welcome flow does not just lose the immediate revenue from those new subscribers; it reduces their lifetime engagement with your brand, making every subsequent email less effective. A list that has not been cleaned does not just have low open rates; it damages your sender reputation, which reduces deliverability for all your emails, including the ones going to engaged subscribers.
The cumulative cost of email marketing mistakes is almost always higher than brands realise, because the effects are interconnected and self-reinforcing. Fix the fundamentals and everything improves simultaneously.
Mistake 1: No welcome flow
A welcome flow is the single highest-performing automated email sequence for ecommerce brands. New subscribers have just expressed interest in your brand — their engagement and purchase intent will never be higher than in the first 24-48 hours. If you do not have a welcome flow, you are wasting the most valuable moment in the customer relationship.
An effective welcome flow typically includes 3-5 emails over 5-7 days: an immediate welcome with a brand story and any promised incentive, followed by emails that introduce your best products, share social proof, address common objections, and create a clear path to first purchase. On Klaviyo, welcome flows routinely generate 10-20% of total email revenue for well-optimised stores.
For detailed guidance, see our post on creating a Klaviyo welcome series.
Mistake 2: Sending generic blasts to everyone
Sending the same email to your entire list is the email marketing equivalent of standing in a crowded room and shouting. Some people will hear you, but most will tune you out, and a few will leave the room entirely.
Your subscribers have different interests, different purchase histories, different levels of engagement, and different stages in their relationship with your brand. A customer who bought a premium skincare set last week does not need the same email as someone who browsed your sale section once and never returned.
Segmentation does not need to be complex to be effective. Start with basic segments: engaged vs. unengaged subscribers, customers vs. non-customers, recent buyers vs. lapsed buyers, and product category interest segments. Even these basic segments will significantly improve open rates, click rates, and revenue per email. Our guide to segmenting your email list properly covers the practical details.
Mistake 3: A single abandoned cart email
Abandoned cart recovery is typically the second-highest revenue flow after welcome series, but many brands send just one generic reminder email and leave it at that. A single email recovers some revenue, but a well-structured sequence of 2-3 emails, spaced appropriately and escalating in urgency and incentive, can recover 2-3x more.
An effective abandoned cart sequence typically includes: a first reminder at 1-2 hours (no discount, just a helpful nudge), a second email at 24 hours (adding social proof and addressing common objections), and optionally a third email at 48-72 hours (with a time-limited incentive if your margins allow it). Each email should include the specific products abandoned, clear pricing, and a direct link back to the cart.
Mistake 4: No list segmentation
This extends beyond just campaign sends. Brands that do not segment are typically also not suppressing unengaged contacts from their flows, not personalising product recommendations, and not tailoring their messaging to different customer profiles.
The consequence is lower engagement rates across the board, which damages sender reputation, which reduces deliverability, which further reduces engagement — a vicious cycle that gradually erodes the effectiveness of your entire email programme.
At minimum, maintain these segments: VIP customers (top 10% by revenue), active customers (purchased in last 90 days), at-risk customers (last purchase 90-180 days ago), lapsed customers (no purchase in 180+ days), engaged non-customers (active subscribers who have not yet purchased), and unengaged contacts (no opens or clicks in 90+ days). These segments should drive both your flow targeting and your campaign sending strategy.
Mistake 5: Ignoring deliverability
You can write the most compelling email in the world, but if it lands in the spam folder, nobody will see it. Deliverability is the foundation that everything else depends on, yet it is the area most brands pay the least attention to.
Common deliverability killers include sending to unengaged subscribers (mailbox providers track engagement and penalise senders with low open rates), failing to authenticate your sending domain (SPF, DKIM, and DMARC records), sending from a shared domain instead of a dedicated one, sudden spikes in send volume, and high spam complaint rates.
For a practical guide to fixing deliverability issues, read our post on improving Klaviyo deliverability. The short version: clean your list regularly, authenticate your domain, segment your sends, and monitor your deliverability metrics weekly.
Mistake 6: Never testing anything
Most ecommerce brands send emails based on assumptions and best practices rather than data from their own audience. A/B testing subject lines, send times, content formats, and offers is how you discover what actually works for your specific subscribers.
The most impactful tests for ecommerce email are: subject line testing (which directly impacts open rates), send time testing (which affects both open and click rates), content format testing (text-heavy vs. image-heavy, long vs. short), and offer testing (percentage discount vs. fixed amount, free shipping vs. product discount).
Test one variable at a time, use statistically significant sample sizes, and document your findings. Over time, testing compounds your email performance in the same way that compound interest compounds savings — each improvement builds on the last.
Mistake 7: Over-discounting in every email
If every email you send contains a discount code, you are training your customers to never buy at full price. This is one of the most common and most damaging email marketing habits in ecommerce.
Discounts have a role in specific contexts: incentivising first purchases in welcome flows, recovering abandoned carts when margins allow, winning back lapsed customers, and driving volume during genuine seasonal events. But the majority of your email content should build brand value and drive full-price purchases through product education, new arrivals, customer stories, and content that reinforces the quality and desirability of your products.
A good rule of thumb: no more than 20-30% of your emails should contain a discount. The rest should give people a reason to buy that has nothing to do with price.
Mistake 8: Not designing for mobile
Over 60% of email opens happen on mobile devices. If your emails are not designed mobile-first, you are optimising for the minority of your audience and frustrating the majority.
Common mobile email issues include images that are too wide for mobile screens, text that is too small to read without zooming, CTA buttons that are too small to tap accurately, and layouts that break or become confusing on narrow screens. Every email should be tested on mobile before sending — most email platforms including Klaviyo have built-in mobile preview tools.
Mistake 9: No post-purchase flow
The period immediately after a purchase is another high-value window that most brands waste. A post-purchase flow serves multiple purposes: it reinforces the customer's decision (reducing buyer's remorse and returns), provides useful information about their order, introduces complementary products, and solicits reviews that become social proof for future customers.
An effective post-purchase flow might include: an immediate order confirmation with brand messaging (not just the transactional receipt), a delivery follow-up with product care or usage tips, a review request timed to arrive after the customer has had time to use the product, and a cross-sell recommendation based on their purchase.
Mistake 10: Setting flows and forgetting them
Automated flows should not be "set and forget." They need regular review and optimisation to remain effective. Product images become outdated, offers expire, best-selling products change, and what worked six months ago may not work today.
Review your flows quarterly at minimum. Check performance metrics against benchmarks, update product recommendations, refresh creative, and test new approaches. Flows that were high-performing when created will degrade over time without maintenance. See our guide on why set-and-forget fails for Klaviyo flows.
How to fix these and move forward
If you recognised several of these mistakes in your own email programme, do not try to fix everything at once. Prioritise based on revenue impact:
- First: Fix your flows. Welcome flow, abandoned cart, and post-purchase — these three flows alone should generate 30-50% of your email revenue. Get them right first.
- Second: Clean your list and fix deliverability. Better deliverability improves everything else. Remove unengaged contacts, authenticate your domain, and establish a regular cleaning schedule.
- Third: Implement basic segmentation. Even simple segments dramatically improve campaign performance and subscriber experience.
- Fourth: Start testing. Begin with subject line tests on your highest-volume campaigns and expand from there.
- Fifth: Review and optimise monthly. Treat email marketing as an ongoing optimisation discipline, not a periodic project.
Email marketing done well is the most profitable channel available to ecommerce brands. The gap between average and excellent email performance is enormous, and it is almost entirely a function of avoiding these common mistakes and committing to systematic improvement over time.
If you want a professional assessment of your email marketing programme and a clear plan to improve it, get in touch. We manage Klaviyo for dozens of ecommerce brands and know exactly where the revenue opportunities are hiding in your account.