Case Study: Why Catalyst Pet Blocked Full-Margin Customers to Protect Their Team

When the Right Move Is to Fire a Customer

Most ecommerce fraud prevention content focuses on customers who are trying to extract money from the merchant — discount abusers, chargeback artists, serial returners. Catalyst Pet's story is a different one.

Their problem was not money. It was morale. They had a small set of repeat customers who paid full price, shipped to the same addresses, and generated consistent revenue — and who treated customer service staff so badly that it was damaging the team's ability to function.

Not occasional friction. Not one-off bad days. A consistent, repeated pattern of verbal abuse aimed at support reps: name-calling, personal attacks, threats of public retaliation. The kind of interactions that stay with people after the shift ends, that make Monday harder, and that push good employees to start looking for other jobs.

After internal discussion, Catalyst Pet's leadership made a decision that a lot of brands struggle to make. The revenue from those customers was not worth the cost to the team. They wanted those customers gone.

The question was how to enforce that decision when Shopify does not have a native way to block a customer, and when those customers were experienced enough to know that creating a new email address would let them keep ordering.

Why Email Blocking Alone Does Not Work

The most common tactic merchants use to "block" a customer is to blacklist their email address. It is the approach that works natively inside most apps and email platforms. Set a flag on the email, and future orders using that email get flagged or rejected.

The problem is the same structural issue that underlies every piece of fraud prevention content on this blog: email addresses are free and unlimited. A determined customer who knows they have been cut off will spend thirty seconds creating a new Gmail address, placing the order again, and expecting it to go through. They know your products. They know your checkout. They do not need your account to shop.

For a customer who was already abusive enough that the brand wanted to block them, the likelihood of them simply accepting the block and walking away was low. The likelihood of them cycling through email addresses to keep ordering — and, in the process, continuing to interact with the same support staff who were already struggling with them — was high.

A real block had to be tied to the person, not to a single identifier.

How the CustomerGenius Blocklist Works

The blocklist feature was built to solve exactly this problem. It ties a block to the customer's identity across multiple signals rather than to a single email address. The mechanism is intentionally simple:

That is the entire configuration. From that point forward, CustomerGenius monitors every new order across the store and checks whether the order's identifiers match the blocklisted profile. The check runs across the same five signals that power the app's discount fraud detection:

When enough signals match a blocklisted customer, the new order is automatically refunded through the Shopify API. The refund happens within seconds of the order being placed — before the warehouse pulls the product, before any support interaction occurs, before the blocked customer has any opportunity to get back in touch with the team that the block was meant to protect.

Why This Is the Right Shape for the Problem

For Catalyst Pet, the blocklist feature did something that no amount of internal policy could have done on its own. It enforced the decision without requiring any action from the support team.

In a typical "we do not want to serve this person anymore" situation, the burden falls back on customer service. The rep recognizes the name or email, escalates to a manager, gets confirmation that the customer is on the no-serve list, and then has to manage the refund, the communication, and the fallout. The person the policy was meant to protect is the same person having to invoke it — every time the blocked customer comes back.

With the blocklist tag set, none of that happens. The order is refunded automatically. The team does not see the ticket. They do not have to re-engage with the customer. They do not have to absorb another round of the behavior that got the customer blocked in the first place. The decision is made once, and it enforces itself from that point on.

And critically, because the block ties to the customer's identity rather than a single email address, the customer cannot simply open a new Gmail account to get around it. If they ship to the same address, it is caught. If they reuse their phone number, it is caught. If their name is even fuzzy-similar to the blocklisted profile, it is caught.

Results: Protected Team, Enforced Decision

After Catalyst Pet applied the blocklist tag to the handful of accounts they wanted removed, the decision stuck. New orders from those customers — under new email addresses, in some cases — were caught, refunded, and closed out without any support interaction. The customers had been told they were no longer welcome, and the system enforced that without requiring the team to have the conversation again.

The revenue impact was real. These were full-margin, repeat customers, and blocking them meant permanently removing that revenue from the business. Catalyst Pet's leadership decided that tradeoff was the correct one. A business whose customer service team is being eroded from the inside has a bigger problem than a revenue line item.

The morale impact showed up quickly. Support tickets from those accounts stopped appearing. The team did not have to brace for another round of hostility when a familiar name hit the queue. Time that had been spent managing difficult interactions went into responding to customers who were pleasant to work with.

When to Use the Blocklist vs. Fraud Detection

CustomerGenius's discount fraud detection and its blocklist feature handle different shapes of problem, and it is useful to think of them as complementary tools rather than overlapping ones.

Fraud detection is pattern-based. It watches discount codes or tagged promotions and scores incoming orders for duplicate-identity patterns across multiple signals. It does not know in advance which customers are going to be bad actors — it finds them based on behavior.

The blocklist is identity-based. The merchant has already decided that a specific customer should be blocked, for whatever reason, and the feature enforces that decision going forward. The behavior that led to the decision can be anything: abusive interactions, confirmed fraud from a prior order, chargeback history, competitor activity, serial returns, or a simple business-relationship decision.

Most merchants use both. Fraud detection handles unknown bad actors. The blocklist handles the known ones. Neither requires the other, and the two run independently — but together, they cover almost every scenario where a merchant wants a customer removed from their order flow.

Other Cases Where the Blocklist Fits

Catalyst Pet's situation — blocking customers to protect team morale — is one of the less common use cases, but it is the one that most clearly shows what the blocklist is for. A short list of other patterns where merchants have applied it:

In every case, the shape of the problem is the same. The merchant has made a decision about a specific person, and they need that decision to stick across future orders regardless of what identifiers the person uses.

The Takeaway

Revenue is not always the right yardstick for customer value. A customer who pays full price and treats your team like dirt is not a profitable customer once you account for turnover, training costs, and the intangible cost of the work environment itself. Most brands know this. Most brands struggle to act on it because the tools they have only block email addresses, and email addresses are trivial to replace.

Catalyst Pet's leadership made a clear call about which customers they wanted to serve, and CustomerGenius's blocklist gave them the mechanism to enforce it. The block works across email, phone, address, and name — so when a blocklisted customer returns under a new identity, the system catches them anyway.

If your store has a short list of customers you would rather not serve — for any reason — the blocklist is the feature built for that decision. See how it fits alongside discount fraud detection on the CustomerGenius pricing page, or install CustomerGenius from the Shopify App Store to start protecting your team and your margins together.