Open rates used to be the headline metric every email marketer led with. Then Apple introduced Mail Privacy Protection, which pre-loads email content — including tracking pixels — regardless of whether a recipient actually opens the message. Overnight, open rates for a significant portion of audiences became inflated and unreliable as a primary performance indicator.

This doesn’t mean open rates are worthless. They still provide directional signal, particularly for non-Apple audiences. But if you’re optimising your Klaviyo strategy primarily around open rates, you’re navigating with a partially broken compass. The brands getting the most from their email programmes have shifted their focus to metrics that paint a more accurate picture.

Click rate is the first place to look. A subscriber who clicks has demonstrated genuine intent — they saw something relevant enough to act on. Click-to-open rate, which measures clicks as a proportion of opens rather than total sends, gives you a cleaner read on content relevance because it filters out the noise of inflated open numbers. If your click rates are healthy, your content is working regardless of what the open rate says.

Revenue per recipient is arguably the most important metric in a commercial email programme. It cuts through everything — deliverability variables, engagement fluctuations, list size changes — and tells you directly what each send is worth. Tracking this consistently across campaigns and flows allows you to make genuinely informed decisions about what content, timing, and audience targeting drives results.

List growth rate matters because email lists decay naturally over time. Subscribers change email addresses, lose interest, or simply move on. A list that isn’t actively growing is effectively shrinking in value. Tracking net list growth — new subscribers minus unsubscribes and suppressions — gives you a clear picture of whether your acquisition efforts are keeping pace with natural attrition.

Unsubscribe rate, while often viewed negatively, is a useful signal when tracked in context. A spike in unsubscribes after a particular campaign tells you something about relevance or frequency. A steadily increasing unsubscribe rate over time suggests a deeper mismatch between what your list expected and what you’re delivering.

The deeper issue behind declining performance is usually one of three things: list fatigue from sending too frequently or without enough relevance, deliverability problems causing emails to land outside the inbox, or content that isn’t connecting with the audience it’s reaching.

List fatigue is addressed through smarter segmentation — not emailing everyone every time, and ensuring that what you do send is earned by its relevance. Deliverability issues require a technical audit of your authentication setup, sending domain, and list hygiene practices. Content disconnects are harder to diagnose but often come down to a mismatch between the promise made at signup and the reality of being on your list.

Klaviyo gives you the data to diagnose all three. The platform’s analytics allow you to drill into performance by segment, by flow, by campaign, and over time — giving you a granular view of where performance is healthy and where it’s leaking. The brands using this data actively, rather than glancing at top-line numbers, are the ones consistently improving.

If your Klaviyo performance has plateaued or is trending in the wrong direction, the answer is rarely to send more. It’s to send smarter. Get in touch if you’d like a fresh set of eyes on what your data is telling you.