The people who never open your emails are killing your deliverability

There's one thing I see with almost every new client we pick up in a CRM audit. The list is 80,000, 120,000 contacts, the founder is super proud of the number, and when you dig in you realise half that list hasn't opened an email in eight months. And it's exactly that half that's wrecking the performance of the other half.

We tend to think an inactive contact is no big deal, that worst case they don't open and it costs nothing. Wrong. It costs a lot, it just doesn't show up on your Klaviyo invoice.

Email deliverability, what it actually means

Before we go further, a quick vocabulary check because people mix these two up constantly. There's delivery rate and there's deliverability, and they're not the same thing.

Delivery rate just measures whether the email was accepted by the mailbox provider's server. It didn't bounce, it didn't come back. Deliverability comes after that, and it's the one that actually matters. It's whether your email lands in the main inbox, or ends up in the promotions tab, or worse, in spam.

You can have 99% of emails delivered and terrible deliverability. The email is "delivered" on the Klaviyo stats side, but nobody sees it because it's buried in a tab your customer never opens. Most brands get fooled right here, they look at delivery rate, they feel safe, when the real problem is somewhere else entirely.

Gmail and Yahoo are grading you constantly

A lot of people think deliverability is some obscure technical thing. Honestly, the basic principle is dead simple. Gmail and Yahoo watch what people do with your emails. Do they open? Do they click? Do they reply? Or do they let them rot in the inbox without ever touching them?

When a big chunk of your list ignores your emails for months, mailbox providers read that as a signal. To them the message is clear, your emails aren't wanted. And from there they start routing some of your traffic to spam. Not just for the inactives. For everyone. Including your best customers, the ones who open every time and buy.

And that's the whole trap. You can have 15,000 golden contacts who love your brand, and drag them down with 60,000 ghost contacts that have been sitting in your list for two years.

Why do my emails land in spam when the content is good

Because content is only part of the story. You can polish your subject line, clean up your HTML, avoid the words that trigger filters, but if your sender reputation is in the red, your beautiful email still ends up in spam.

What drags that reputation down is mostly overall engagement across your domain. On paper, sending to more people means more reach, so more sales. Volume logic. Except the mailbox provider doesn't think that way. It thinks in average engagement rate. If your open rate collapses because you're blasting people who don't care, you degrade your reputation, and that means you reach the people who matter less effectively.

One technical detail that matters too, fonts. In emails you can't use custom fonts, they're not rendered correctly by mailbox providers and they can quickly turn into an ugly render that trips the filters. Stick with Arial or Helvetica, it's not sexy but it works everywhere.

I've seen accounts where we cut 40% of the list and CRM revenue went up the following month. No magic involved. The emails were just finally landing in the main inbox instead of the promotions tab or spam.

How to spot the contacts that are costing you

The way we usually slice it is by activity window. In Klaviyo you build clean segments based on last open or last click.

You split by activity. Recently active, opened or clicked in the last 90 days, that's your core list, you talk to them normally. The lukewarm ones, between 90 and 180 days with no interaction, that's where you ease off and start working them differently. And the ones really dragging you down, the deeply inactive, nothing for more than 6 months.

One important detail on opens. Since Apple Mail Privacy Protection, open rate has become a pretty garbage signal, Apple pre-loads the pixels and artificially inflates your opens. So if you can, segment on clicks instead. Clicks don't lie, either the person clicked or they did nothing. Someone who hasn't clicked a single time in 6 months, you can be almost certain they're not reading you anymore.

How to test your deliverability before it spirals

You can't fly blind. There are two or three simple ways to know where you stand.

First, sign yourself up to your own list with a Gmail address, a Yahoo, an Outlook, and watch where your campaigns land. Main inbox, promo tab, or spam. Actually do it, it's the most telling test out there and it's free.

Second, watch your complaint rate, the people marking you as spam. If it climbs, that's the clearest red flag your list is going off the rails. If opens suddenly collapse across the board, same thing, your reputation is taking a beating and you need to act fast.

When deliverability drops sharply, the cause is almost always the same, either you sent too many emails at once to a list that's too cold, or a big inactive segment has been dragging you down for weeks. You cut sends to the inactives, you slow the pace, and it repairs itself gradually.

The win-back, and especially the step everyone skips

Before you delete anyone, you try one last thing. You run a win-back on everyone who hasn't opened or clicked in months. A sequence of two or three emails, spread over about ten days.

On the subject line, no need to reinvent the wheel, but this is where it's won or lost, so put some care into it (we go deeper in our best practices on email subject lines). Something direct, a bit honest, like "Should we part ways?" or "You disappeared, now what?". You can drop an offer in if your margin allows, but it's not mandatory. All you want is to trigger a click, nothing else.

And now the step 90% of brands forget. The ones who don't even respond to the win-back, you stop emailing them. You pull them out of your regular sends. Full stop.

It's psychologically hard, I know. You paid to acquire these contacts, it feels like throwing money away. But keeping them active in your campaigns is worse than letting them sleep. Every email you send to a dead contact costs you a little reputation with the living ones.

What we do in practice is move them into a "suppressed" segment that we no longer target in campaigns. They stay in the account, they can come back if they buy in-store or return to the site, but they no longer weigh on your daily deliverability.

The special case of retail brands

If you have physical stores, the trap is even nastier. You have tons of people who signed up at the register, who know the brand through retail, but who will never open an email. They were there to buy in-store, not to get newsletters. The result, you end up with a huge proportion of structurally inactive contacts in your list.

Here, cleaning house is even more vital. A retail subscriber who has never opened a single email, you suppress them without hesitation. They already know you, you'll see them again in-store, but they have no business being in your online campaigns.

Stop looking at the size of your list

The real question, how many actually read you. Not how many you have. A list of 30,000 engaged contacts is worth ten times more than a list of 100,000 where 70% are ghosts.

You also need to look at the other end of the pipe. If your root problem is that you're funneling in loads of low-quality contacts, cleaning up or not, you're just patching a leak. Better to work upstream on sign-up forms that bring in genuinely interested people than to spend your life cleaning up behind them.

Second project, go all-in on automated flows instead of manual blasting. An abandoned cart flow, a welcome flow, a best-seller flow, they reach people at the right moment and self-adjust to their engagement. That's exactly what we build on the Retain side, because CRM profitability comes from there, not from the number of newsletters you send.

In practice, where to start to improve your email deliverability

If you're reading this and you know your list is packed with inactives, here's the order I'd tackle it in.

You segment on clicks first, not opens, to get a real picture of who's actually listening. You identify everything that hasn't clicked in 6 months. You run a two or three email win-back on that segment. The ones who react, you fold back into your normal list. The ones who stay silent, you suppress from your sends.

Run this cleanup every quarter and you'll watch your deliverability climb back up. And the CRM revenue follows right behind, mechanically. You send to fewer people and the number goes up anyway. Simply because the emails land with the people who read them.