Why your Klaviyo open rates are dropping (and what to do about it).

Two things happened to email in 2024–2025 that are still working their way through the data. Apple Mail Privacy Protection became near-universal among iOS users, and Gmail tightened its sender requirements in a way that quietly demoted any brand that wasn’t running clean DKIM, SPF, and DMARC alignment.

The combined effect: your open rates aren’t dropping because your subject lines got worse. They’re dropping because the measurement got worse, and because Google and Apple are filtering more of your audience away before they even see the email.

Here’s what to actually do about it.

First: stop optimising open rates

Open rates are now a measurement artefact more than a behaviour signal. Apple MPP inflates them (pre-fetched opens register as real). Gmail filtering suppresses them. Neither is signal.

If you’re still optimising subject lines primarily based on open rates, you’re optimising for a number that’s partly fictional. Switch your primary metric to click-through rate (CTR) for engagement and revenue per email sent for performance.

Check your deliverability setup

Before diagnosing content or segmentation, verify the technical foundation:

DKIM — authenticated? Check in your Klaviyo account settings or use MXToolbox.
SPF — your sending domain should have an SPF record that includes Klaviyo’s sending infrastructure.
DMARC — must be set to at least p=none to avoid demotion. p=quarantine or p=reject is better.
Domain warmup — if you’ve recently moved domains or changed sending infrastructure, you need to warm the new domain gradually.

If any of these are missing, fix them before changing anything else. Deliverability problems look like open rate problems but they’re not.

List hygiene

The second most common cause of declining open rates is a growing disengaged subscriber list. Email providers notice if you’re sending to people who never engage — it’s a signal that your list quality is poor.

Run a list clean every quarter:

Suppress anyone who hasn’t opened or clicked in 180 days
Run a win-back flow before suppressing (one email: “still interested?”)
Hard-remove unsubscribes and bounces immediately

A smaller, cleaner list will deliver higher apparent open rates and better deliverability than a large, dirty one.

What to measure instead

Old metric	Better metric	Why
Open rate	Click rate	Less affected by MPP
Open rate	Revenue per recipient	Ties email to actual outcomes
List size	Active subscriber count	Quality over volume
Campaign open rate	Flow open rate	Flows are warmer; meaningful comparison

The honest summary

Declining Klaviyo open rates in 2026 are almost always one of three things: MPP inflation masking real decline, deliverability degradation from technical issues, or a genuinely disengaged list that was never cleaned. The fix depends on which one it is.

If you want help diagnosing which problem you have, we work with six D2C brands at a time on lifecycle as one of four surfaces inside the engagement.