Rescue a cold list before re-engagement

Email addresses decay ~23% per year — people change jobs, close ISP accounts, abandon providers. A list that was 96% deliverable last spring is maybe 75% deliverable today. Re-engagement without a fresh validation is the number-one cause of sender-reputation collapse we see.

1. 1

   Isolate the cold cohort

   Left sidebar → Audience → Lists & segments → click Create segment (top-right). In the Segment builder, pick What someone has done (or not done) → Received Email zero times in the last 180 days (or whatever window matches your definition of "cold").
2. 2

   Run Securify on that segment

   Full SMTP probe — you want the freshest verdict you can get.
3. 3

   Send the re-engagement ONLY to the clean survivors

   New campaign → audience = cold segment AND securify_status equals deliverable. Everything else is either dead or low-quality signups that should stay parked.
4. 4

   Decide what to do with the undeliverables

   Two valid options: suppress them from all future sends (safer for reputation), or delete them from Klaviyo to reduce your profile count (cheaper if you pay per-profile). Klaviyo's profile delete is permanent — we recommend a standing suppression segment first.