How do you separate cold from warm audiences to rebuild?

Your sender reputation is in recovery mode. The worst thing you can do right now is blast your entire list and hope for the best. The best thing you can do is start small, prove your good intentions to mailbox providers, and expand from there. That means segmenting by engagement before you send a single recovery email.

Here's how to think about it. You're not splitting your list into personality types. You're splitting it by the last time someone actually interacted with your emails, because that's the data mailbox providers use to judge you.

The three tiers

Hot (0-30 days): These are the people who opened, clicked, or replied in the past 30 days. They're your most engaged subscribers, and they're the most likely to keep engaging now. Mailbox providers notice that positive activity. Start here and only here.

Warm (31-90 days): These folks showed interest recently but haven't touched anything in a while. They're not gone, but they're not certain either. You can add them once your metrics from the hot tier are looking healthy (think consistent open rates above 20%, low spam complaints, no major bounce spikes).

Cold (91+ days): These subscribers haven't engaged in three months or more. They carry real risk. Some addresses may have gone dormant, some may belong to people who genuinely forgot about you, and some could be spam traps by now. Do NOT fold them into your recovery sends. Treat them as a separate project once your reputation has stabilized.

How to build these segments in your ESP

Every major ESP stores last open date and last click date as contact fields. You're going to filter on those. Here's the rough logic:

• Mailchimp: Use the Campaign Activity segment filter. Set it to "opened" or "clicked" within the past 30 days. Save that as your Hot segment. Then build a second segment for 31-90 days. The Cold group is everyone outside that window.
• Klaviyo: Create a Segment using the "Has been in a list" and "Properties about someone" conditions. Filter on "Last Email Open" within the relevant date range. Klaviyo's predictive analytics can also flag likely churn risk, which helps you decide who's borderline warm vs cold.
• ActiveCampaign: Use the Contacts filter and combine "Last Open Date" and "Last Clicked Date" conditions. Tag each tier so you can manage them separately across campaigns.
• Brevo: Build a segment under Contacts using the "Email engagement" filter. You can set open or click behavior within custom date ranges.

Now most other ESPs follow a similar pattern. If yours doesn't have a native engagement date filter, you can export your contacts, sort by last open date in a spreadsheet, and re-import with a "Tier" tag attached.

The recovery cadence

Week one and two: hot tier only. Send one email. Watch your open rate, complaint rate, and bounce rate closely. If those numbers hold steady and look healthy, you're good to keep going.

Weeks three and four: if hot is behaving well, add your warm tier. Keep your sending volume modest. You're not trying to catch up on missed sends. You're trying to rebuild trust.

Cold tier: don't rush this. A proper re-engagement campaign for cold subscribers is its own project with its own sending subdomain, strict suppression rules, and a clear exit condition (if they don't respond to three well-spaced sends, suppress them permanently).

Now one thing worth knowing: opens alone aren't the most reliable signal anymore since Apple MPP inflates them artificially. If you can, weight clicks and replies more heavily than opens when deciding who counts as "hot." A click or a reply is a real human action. An open might not be.

If you're not sure which tier your list falls into or your ESP's engagement data is incomplete, we can help you sort it out. Drop us a message on the SOS hotline and we'll take a look with you.