Klaviyo detectives: A signal-based playbook to find (and fix) email fatigue

As a fellow email marketer or Klaviyo enthusiast, do you recall that moment when a once-loyal subscriber turns into a ghost? 

Opens shrink, clicks vanish, revenue from flows goes flat, and your inbox feels like you’ve been quietly excommunicated from your own audience. That’s not drama. That’s fatigue.

We learned to spot it the hard way, a client with “good” averages and terrible outcomes. On the surface, their account looked healthy. 

But beneath the averages, certain emails were quietly eating engagement. Once we dug in, the pattern was obvious and fixable. 

This post is a step-by-step guide to the exact, practical method we use within Klaviyo to identify where fatigue begins, why it spreads, and what to adjust so your audience doesn’t tune you out.

(Yes, this is written by a Klaviyo nerd who’s seen too many “over-send” horror stories. You’ll get frameworks, real signals to watch, and some practical guiderails to play by.)

Let’s hit the gas, shall we?!

An insight into why email fatigue matters and why you shouldn’t brush it under the carpet!

Email fatigue isn’t a fuzzy feeling or that niggling scratch on your nose; it’s measurable and expensive. 

Klaviyo itself defines email fatigue as when “your subscribers start to feel overwhelmed by the number of emails they receive from you,” leading to lower engagement, higher unsubscribe, spam complaints, and a damaged sender reputation.”

In practice, what does that look like? Here are a few signs to watch out for:

• A steady decline in open rates over weeks or months
  
• Click-through rates (CTR) are falling off even when opens hold
  
• A spike in unsubscriptions or spam complaints tied to specific sends
  
• An uncharacteristic exit from flows before conversion
  
• Rising bounce or suppression rates
  
• Stagnating or negative ROI despite “normal” open/click metrics

Honestly, consumers are tired of message overload: surveys over the past few years have repeatedly shown that a majority of people feel overwhelmed by the volume and frequency of marketing emails. A round-up of consumer research from one industry found that 74% of people report feeling overwhelmed by email overload. 

And the consequence is direct: recent research from Optimove shows that many consumers actively unsubscribe or disengage when brands overwhelm them. The report found large percentages (70%) of consumers have already unsubscribed from brands because of excessive messaging, and personalization (when done right) materially improves open and purchase behavior. In short, relevance and frequency both matter, and when you get either wrong, people will leave. 

Klaviyo, like most responsible ESPs, recommends segmentation, frequency testing, and flow filters as core defenses against fatigue. Those platform controls aren’t optional; they’re the tools you use to make “less but better” actually happen. 

To surmise, email fatigue is very real. However, the challenge is not just knowing it exists; the real skill is identifying where within your journey the fatigue is triggered. That’s where the Signal-Based Review comes in.

Decoding the central idea ~  Spot the signals, cease to guess

Most teams treat dips in open rates or an uptick in unsubscribes as isolated problems. We prefer thinking like a detective and following the signals. The Signal-Based Review is a concise, repeatable audit that reveals where and how fatigue emerges within your journeys, not just that it exists.

Here’s the short checklist we run when we take over a Klaviyo account (followed by the how and why):

1. Map every active flow + recent campaigns and highlight overlaps.
   
2. Export per-email metrics (open, click, unsubscribe, spam complaints, bounces).
   
3. Spot step-to-step drop-offs inside flows and spikes tied to specific sends.
   
4. Measure the per-contact send frequency over 7, 14, or 30 days.
   
5. Run a simple segment test (engaged vs. unengaged).
   
6. Act surgically: add filters, caps, suppressions, and small content tweaks, then re-measure.
   

Read the full method below, because it’s where the work gets interesting.

The Signal-Based Review method: Diagnosing fatigue with precision

You may think of this method as running a diagnostic scan on your Klaviyo account. You’re not gutting everything, you’re just targeting the pain points. Below is the step-by-step approach we use when auditing.

Step 1 — Map journeys (like you’re drawing a subway map)

You can start by listing every active flow (e.g., welcome, abandoned cart, browse abandonment, post-purchase, win-back, review request) and all campaigns sent within the last 30–60 days. Draw overlap lines: Where does a campaign intersect with people who are already in the mid-flow stage? Where do flows send promotional mail while a campaign is also live?

Fatigue often results from clustering, where the same person receives three messages from different automations within a short window. You can’t fix fatigue if you don’t see the collisions.

Step 2 — Pull per-email performance

Export, for every single email, the open rate, click rate, unsubscribe rate, spam complaints, delivered vs. bounced, and list-health signals. Put them in a sheet with flow step order. This provides a clear timeline for each contact journey.

So, account-level averages hide problem emails. When you line up steps 1, 2, and 3, anomalies jump out.

Step 3 — Find the hotspots (the simplest diagnostics)

Compare step-by-step in flows. A steep open rate drop between two consecutive emails? Flag it. Opens okay, but clicks fall? Flag it. A sudden spike in unsubscribes or complaints related to a single send? Red light.

These hotspots identify where subscribers are saying “enough.”

Step 4 — Measure cumulative pressure (sends per person)

This is the secret sauce. Use Klaviyo’s recipient activity or a segment that counts how many emails each profile received in the last 7/14/30 days. If someone receives 4–6 messages in a week and shows no engagement, they’re in a “danger” bucket, and continuing to message them is wasteful (and risky for deliverability).

Fatigue is cumulative. One email might be fine; the tenth in two weeks is not.

Step 5 — Segment test (engaged vs unengaged)

Create two test groups:

• Engaged: opened/clicked in the last 30 days
  
• Unengaged: no opens/clicks in 60+ days
  

Send the same email or hold it, and compare CTR, unsubscribes, and conversions. If the unengaged group unsubscribes at much higher rates, you’ve proved that segment needs suppression or a gentler re-engagement path.

You want to be surgical; remove or re-permit the people who are actively harming deliverability.

Step 6 — Act, measure, repeat

Now for the fun part: add flow filters (e.g., “skip if received 3+ emails in last 7 days”), insert waits, build a fatigue suppression segment, and test subject line/content refreshes where drop-offs occurred. Run the same signal audit again after 2–4 weeks to see if there is improvement.

Klaviyo gives you the tools to use flow filters and Smart Sending to block overlapping sends and prevent unnecessary touches.

Once changes roll out, you don’t just hope; you re-run the Signal Review quarterly to catch new fatigue zones before they become revenue sinks.

Why this method works (and beats guesswork)

You might ask, why not just rely on “gut” or only track open/click trends at the account level? Here are three reasons this signal-based approach is far stronger:

1. Precision, not broad strokes: You identify which email, which step, which segment causes fatigue, not just “our account performance is down.”
   
2. Cumulative insight: Metrics like “emails per user in last week” let you see fatigue that doesn’t yet show as a crash in opens.
   
3. Evidence-led iteration: Instead of hoping “less is more,” you get data-backed decisions on where to cut, pause, or reform.
   

In effect, you’re mapping the weakest link in your journey rather than ripping down the whole structure.

Best practices & extra tips to counter fatigue

Here are some guardrails and ideas we always lean on as we monitor fatigue long-term:

• Audit every quarter — Signals shift as your list grows or as you add new campaigns
  
• Use frequency caps — Max 3–5 total sends per user per week (adjust to your audience)
  
• Warm-up segments — When reactivating lapsed segments, ease them in slowly
  
• Personalize content deeply — Use browsing history, past purchases, affinities, not just “Hello {name}”
  
• Smart sending & time optimization — choose send windows that maximize the chance of engagement rather than blasting at all hours
  
• Re-permission campaigns — periodically ask for consent, offer value, and allow subscribers to control cadence
  
• Suppression over punishment — mark unengaged profiles instead of punishing them forever
  

Use A/B tests smartly — test subject lines, send delays, “skip send” logic only where fatigue might lurk

Email fatigue is preventable!

If there’s one mindset shift we wish every Klaviyo marketer embraced, it’s this:

Fatigue isn’t a failure of “email being broken,” it’s a signal that you’re asking too much too soon.

Your subscribers are real people with inbox limits, attention spans, and changing moods. They won’t tell you directly; they’ll just ghost your senders. But if you listen, via opens, clicks, unsubscribes, and behavior, you’ll see the fault lines.

The Signal-Based Review method gives you a compass, not a silver bullet. But more than guesswork, more than hoping “less sends will help,” it gives you diagnostic precision. 

The road ahead

If you are considering migrating your current ESP to Klaviyo and need some genuine guidance, we suggest reading ~ Klaviyo Migration Checklist: Steps & Best Practices.