A cold subscriber re-engagement campaign isn't about being polite to people who stopped opening your emails, it's about protecting the deliverability of everyone else on your list, and the two goals point in exactly the same direction.
Gmail and Yahoo don't read your emails, but they read what your subscribers do with them, and a subscriber who hasn't opened anything in four months is a signal, not a neutral bystander. Every send to that address that goes unopened, or worse gets deleted without opening, tells the mailbox provider your content isn't wanted, and that reading gets applied to your sender reputation as a whole, not just to that one address.
This is why list size and list quality pull in opposite directions past a certain point. A big list full of cold addresses can perform worse than a smaller, engaged one, because mailbox providers weight engagement more heavily than raw volume when they decide where your next email lands. If your deliverability rate has been sliding, cold subscribers are one of the first places to look.
The 9-word email is a format popularized by marketer Dean Jackson, and it's exactly what it sounds like: a single short line, roughly nine words, sent to cold subscribers asking something like "Are you still looking for [thing they signed up for]?" No links, no images, no formatting, just a plain question that reads like it came from a person, because it did.
It works for a few reasons that stack on top of each other. It's short enough to read in the preview pane, so it gets consumed even by someone who wasn't going to open a full newsletter. It asks a genuine question rather than pitching anything, which lowers the guard people put up against marketing email. And most importantly, it's built to get a reply, not a click, and a reply is one of the strongest positive engagement signals a mailbox provider tracks, far stronger than an open.
The 9-word email works well as an opener, but I'd build it into a short sequence rather than a one-off. Something like three emails over two to three weeks: the plain 9-word question first, then a follow-up a week later that reminds them specifically what they signed up for and offers one clear reason to stay, a resource, a discount, whatever fits your list, and a final email that's honest about what happens next, along the lines of "this is the last email unless you tell us to keep sending."
Keep each one short and keep the ask small. You're not trying to sell anything in a re-engagement sequence, you're trying to get a click, a reply, or an unsubscribe, all of which are more useful to you than silence.
If someone doesn't respond to the full sequence, stop emailing them. This feels counterintuitive when you've spent money or effort acquiring that subscriber, but a cold address that never engages is costing you more in reputation than it's worth in theoretical reach. Suppress or remove anyone who hasn't opened or clicked in the last several months and didn't respond to your win-back attempt.
Before you run a campaign like this again, it helps to prevent the buildup in the first place. A clean list hygiene routine and a proper double opt-in signup process both cut down on how many cold, low-intent addresses land on your list to begin with.
Your list gets smaller and your open and click rates go up, sometimes by a lot, because you removed the addresses that were dragging the average down. That's expected, and it's not a loss, it's your real numbers finally showing through. What matters more is what happens to inbox placement over the following weeks: I've watched clients move out of Gmail's Promotions tab and back into Primary within a month or two of a serious prune, purely because engagement per send went up.
If you've done the pruning and the sequence and you're still not seeing placement improve, the issue is probably upstream of your list, in your authentication setup or sending reputation, and that's worth a proper look through Unbury's free deliverability audit.
A short win-back email, popularized by Dean Jackson, that's roughly nine words long and simply asks a cold subscriber if they're still interested in what they signed up for. It's plain text, no links or design, built to prompt a reply rather than a click.
Most lists use somewhere around 60 to 90 days without an open or click, though the right window depends on how often you send. A weekly newsletter can call someone cold sooner than a monthly one.
It will shrink your numbers on paper, but it usually improves the metrics that actually predict revenue, like click rate and inbox placement. A smaller list that lands in Primary consistently outperforms a bigger one stuck in Promotions or spam.
Run the sequence first. It costs almost nothing and it recovers a meaningful chunk of people who simply got busy rather than lost interest. Only remove the ones who don't respond after a genuine attempt.
If you've already pruned and re-engaged and your emails are still landing in Promotions or spam, the cause is probably technical, not behavioral. Run your domain through the free <a href="/audit">deliverability audit</a> and I'll show you exactly where it's breaking.