The Tool Desk
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1. Choose the flow’s job and trigger
A cross-sell recommends a complementary product after purchase. An upsell, by contrast, typically encourages a higher-value alternative and may fit better before checkout. Klaviyo identifies Placed Order and Fulfilled Order as possible triggers for a post-purchase cross-sell flow; its guidance says the trigger should be one of those events. See Klaviyo’s cross-sell flow guidance.
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Choose the event that matches the customer experience you want to support. A placed-order trigger starts the clock at purchase. A fulfilled-order trigger starts it after the order is prepared for shipment, which may better reflect when the customer is likely to receive or use the item. For a pre-purchase upsell, a viewed-product event may be more appropriate than a post-purchase flow.
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2. Define who qualifies—and who should leave the flow
Base eligibility on the product or SKU that prompted the flow, not just a broad customer category. Then exclude people who already bought the complementary item. Klaviyo’s example cross-sell segment checks that a person ordered one SKU and has zero orders for another; depending on the event data available, product name or variant name may also help classify purchases. See Klaviyo’s cross-sell segment instructions.
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- Entry: The customer purchased the specific product or product group for which the recommendation makes sense.
- Exclusion: The customer has not already purchased the proposed companion item.
- Exit or suppression: A later order or fulfillment makes the recommendation stale or duplicative.
Klaviyo specifically advises using a flow filter to exclude someone who has another fulfilled order since entering the flow. Configure an equivalent exit or suppression rule in your platform so a customer who has already acted does not keep receiving an obsolete recommendation.
3. Pick complementary products, not merely popular ones
Start with what the triggering purchase enables, completes, protects, or replenishes. For example, a cross-sell should make sense in the context of the product the customer bought; a generic best seller is not automatically relevant. Klaviyo describes using a product feed constrained to a category or collection associated with the purchased or viewed item. A product-specific segment or curated pairing can work when a dynamic feed is not practical.
- Remove the item the customer already purchased from the recommendations.
- Check availability so the email does not promote an out-of-stock item.
- Limit the feed to products that fit the original item’s use context.
- Give the customer a clear reason the recommended product belongs with the purchase.
Mailchimp also supports product recommendations based on purchase history for subscribed contacts. Its purchase-history recommendation block has specific data requirements: at least 10 products, 50 customers, and 500 orders in the last year. Those are Mailchimp feature thresholds, not general ecommerce benchmarks. Below them, recommendations may not display in that block; a curated selection or product-based segment is a practical fallback. Details are in Mailchimp’s purchase-history recommendation documentation.
4. Set timing around fulfillment, delivery, and use
There is no evidence-backed universal delay for every store or product. Consider how long shipping takes, when the customer can use the original item, and when the companion item becomes useful. A setup accessory may make sense soon after delivery; a replenishment-related recommendation may depend on when the original supply is likely to run low.
Klaviyo says its built-in product review/cross-sell flow sends the default message 14 days after fulfillment. That is a platform example, not a generally appropriate schedule. Check your own shipping window and customer experience before adopting it. Klaviyo’s post-purchase flow guidance also recommends using purchase data to identify buying cycles for replenishment flows. That same store-specific timing principle can inform cross-sell tests.
5. Branch by customer history
A first-time customer and a returning customer may need different messages. Klaviyo documents branching post-purchase flows by customer history; see its guidance on flow branching.
First-time buyers
Consider whether a brief usage, setup, or care tip should come before a product pitch. The goal is to make the first purchase easier to use and establish context for a later complementary recommendation—not to assume every new customer is ready for another offer immediately.
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If prior purchases show a relevant pattern, a returning customer may be ready for a more direct pairing or a related product they have not bought. Keep the same product-level eligibility and suppression checks in place; purchase history helps shape the message but does not make every recommendation relevant.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.6. Write the email and check it before sending
Use a subject line and preview text that accurately describe the message. In the body, show why the suggested item complements the purchase and link directly to the product or relevant collection. Shopify’s Shopify Messaging email guidance recommends audience-appropriate language, relevant imagery, checking links and discount details with a test email, and keeping important information out of images because some email clients disable them.
Send promotional email only to people who agreed to receive marketing from your store. Shopify states this requirement in its subscriber-list guidance. Before activating the flow, test the links, product availability, any offer details, and the message rendering.
7. Measure the flow using your own store data
After activation, review the automation’s reporting and evaluate outcomes over a defined period. Shopify documents reviewing reports for marketing automations in its Shopify Messaging automation guide.
- Placed orders and revenue per recipient: Did eligible recipients buy after receiving the message?
- Clicks: Are customers engaging with the recommendation?
- Unsubscribes and complaints: Is the message unwanted or poorly timed?
Interpret these measures in light of who qualified for the flow and how your store performed before it. The platform materials cited here do not establish a general causal revenue lift or a benchmark that applies to every store, so treat your own results—not a promised percentage—as the basis for changes.
How to choose a platform for this flow
Platform names are examples of documented features, not a complete comparison. When evaluating tools, check whether they support the order and fulfillment events your store needs, product-level recommendations, suppression and branching, relevant catalog controls, reporting, and integration with your ecommerce stack.
Quick Recap
- Klaviyo: Its help materials cover cross-sell triggers, product feeds, product-based segments, flow filters, timing, and lifecycle branching.
- Shopify Messaging: Shopify documents post-purchase and first-purchase upsell automations, reporting, subscriber guidance, and email-writing practices.
- Mailchimp: Its purchase-history recommendation block can use customer data, subject to the documented minimum catalog and order-history requirements above.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
