If an ad told you that 85% of your site visitors were not getting your abandoned cart emails, would you assume your Klaviyo flows were broken? One of my clients received a pitch like that, and it did exactly what it was designed to do: create doubt.

The product behind the pitch was described as identity resolution. But that term can refer to very different practices, from cleaning up data that customers already gave you to identifying anonymous website visitors who never subscribed to your brand at all. Here is what ecommerce brands need to understand before buying an identity resolution tool.

What Identity Resolution Means in Email Marketing

At its most basic, identity resolution connects different identifiers to one customer profile. Those identifiers might include an email address, phone number, device, browsing session, ad click, or purchase.

The important question is not simply whether a tool offers identity resolution. It is what information the tool is connecting and where that information came from.

Some identity resolution happens entirely within your own first-party data. Other tools use third-party data networks to match anonymous visitors with contact information gathered elsewhere. Those are not the same thing, even when vendors use the same label for both.

How Klaviyo Uses Identity Resolution With First-Party Data

Klaviyo’s version of identity resolution is relatively conservative. It connects identifiers that a customer has already shared with your brand across different channels.

For example, imagine that a long-time email subscriber later joins your SMS list. At first, the phone number may create a separate profile. When that customer checks out and enters both an email address and phone number, Klaviyo can recognize that the two profiles belong to the same person and merge them.

Everyone in that scenario already opted in or directly shared information with your brand. The system is not finding a stranger’s email address. It is cleaning up your existing customer data so that you have a more accurate view of the relationship.

That type of first-party identity resolution can help reduce duplicate profiles, improve segmentation, and make cross-channel reporting more reliable. The consent context stays connected to your brand.

How Website Visitor Identification Works

A different category is often called website visitor identification, visitor deanonymization, or simply identity resolution. These tools attempt to identify people who browse your site without entering an email address or subscribing.

Depending on the vendor, the matching process may use:

• IP addresses
• Device fingerprints
• Ad clicks and browsing sessions
• Purchase activity
• Third-party identity graphs
• Contact information a person gave to another website or app

Some tools focus mostly on reconnecting a person’s activity across devices and sessions after that person has already interacted with your brand. Others rely on massive third-party identity graphs that process large volumes of signals and make probabilistic matches.

Probabilistic matching means inference, not certainty. A tool may conclude that a visitor is likely associated with an email address, but that does not necessarily mean the person supplied that address to your brand or asked to receive your marketing.

This is how certain vendors claim they can place more people into abandoned cart flows. They are not repairing a broken Klaviyo flow. They are expanding the pool of identifiable people beyond the subscribers already available in your email platform.

Why Unsolicited Commercial Email May Be Legal in the United States

The question most brands ask next is obvious: how can a company email someone who never subscribed to that brand?

I am not a lawyer, so this is a general explanation rather than legal advice. At the federal level in the United States, CAN-SPAM generally functions as an opt-out law rather than an opt-in law. It does not automatically prohibit every first commercial email sent without prior consent.

Commercial senders still have obligations. Among other requirements, they cannot use deceptive sender information or subject lines, they must identify commercial messages appropriately, provide a valid way to unsubscribe, and honor opt-out requests.

That legal framework helps explain how this category of identity resolution tool can exist. But legal permission is only one part of the decision. State laws, international privacy rules, platform policies, and the specific way data was obtained may create additional considerations. Get qualified legal advice before treating a vendor’s compliance claims as settled fact.

The Bigger Risks: Deliverability, Trust, and Unclear Revenue

Even when a tactic is technically allowed, that does not mean it is right for your brand.

The most obvious concern is deliverability. Someone who has never heard of your company is more likely to ignore your message, unsubscribe, or mark it as spam. Those negative signals can hurt your sender reputation and affect the emails you send to people who genuinely know your brand and want to hear from you.

Customer trust matters too. An email that appears to know what someone browsed, despite that person never subscribing, can feel invasive. The short-term opportunity to recover a cart has to be weighed against the experience you are creating for a potential customer.

From what my agency has seen in real accounts, however, the biggest practical question is often revenue. We have inherited clients who were already using these tools, either because a previous agency recommended one or because the promise sounded compelling.

These platforms can be expensive. If the tool runs beside your normal browse and cart abandonment flows, you need to know whether it is producing a clear, incremental lift. Vendor dashboards may show attributed revenue, but attribution in isolation does not tell you whether those sales would have happened through your existing email program anyway.

Questions to Ask an Identity Resolution Vendor

The phrase “identity resolution” is not automatically a red flag. The details determine what you are actually buying.

Before signing a contract, ask:

• What identities are you connecting? Are you merging information customers already gave our brand, or finding contact information through outside data sources?
• Where did the email address come from? Ask for a specific explanation, not a vague reference to a proprietary network.
• Where and how did consent occur? Did the person opt in to hear from our brand, another company, or a broader partner network?
• Is the match deterministic or probabilistic? Understand whether the match is based on confirmed identifiers or an inferred likelihood.
• How will these contacts be separated from our opted-in list? You need visibility into segmentation, suppression, and reporting.
• What safeguards protect sender reputation? Ask how the vendor handles spam complaints, unsubscribes, bounces, and suppression lists.
• How will you prove incremental revenue? Request measurement alongside your existing abandonment flows, ideally with a controlled test.
• What happens to the data if we cancel? Clarify retention, deletion, ownership, and ongoing use.

A credible vendor should be able to answer these questions clearly. If the explanation depends on fear, mystery, or a dramatic percentage with no context, slow down.

How to Evaluate the Real Revenue Lift

Do not evaluate an identity resolution tool only through the revenue number in its dashboard. Compare it with the rest of your lifecycle program.

Start with a clean baseline. Review what your current abandoned cart, browse abandonment, and checkout abandonment flows generate before adding another platform. Then define what counts as incremental revenue and how overlap will be handled.

Look beyond top-line attribution. Track:

• Conversion rate and revenue per recipient
• Spam complaints, unsubscribes, and bounce rates
• Changes in sender reputation and inbox placement
• Overlap with existing Klaviyo flows
• Total platform and management costs
• Net revenue after those costs

If possible, use a holdout group so you can compare people who receive the additional messages with a similar group who do not. Without that comparison, it is easy to mistake claimed attribution for actual lift.

A Smarter Identity Resolution Strategy for Ecommerce Brands

My agency does not recommend the category of identity resolution tools designed to email people who were never on your list. The cost can be high, the incremental revenue can be difficult to prove, and the potential damage to deliverability and trust is real.

That does not mean every use of identity resolution is shady. Connecting opted-in customer information across email, SMS, purchases, devices, and sessions can improve your data and customer experience. The distinction is whether you are organizing a direct relationship or manufacturing one through outside data.

If you are considering a visitor identification platform anyway, ask where every identity comes from, how consent works, and how the vendor will prove performance beside your existing flows. Do not let a scary ad convince you that your email program is broken when the product is actually changing who you are willing to email.

The smartest identity resolution strategy starts with clean first-party data, strong opt-in experiences, and abandonment flows built for people who chose to hear from you. If you want help improving an ecommerce email and SMS program that actually drives sales, visit joyjoya.com.