850K Dormant Users Reactivated at 52% Lower Cost

Multi-channel re-engagement campaign for travel OTA across display, social, email and push

The challenge

A leading European online travel agency had over three million registered users, but nearly 40% had gone dormant -- no booking, search or login activity in over six months. Meanwhile, acquiring entirely new customers through prospecting campaigns cost 3.4x more than reactivating an existing one. The untapped revenue sitting in that dormant base was impossible to ignore.

We designed a sequenced cross-channel re-engagement program that systematically moved users from passive to active. Using DV360 for programmatic display and The Trade Desk for social retargeting, combined with personalized email and push notifications, we built a progressive funnel where each channel activated only when the previous one registered engagement. CPM-based display drove initial recall at low cost, CPC social ads deepened engagement, and CPA-based email and push converted the most responsive users into bookers.

Marketing team planning re-engagement strategy

How we delivered it

We built a sequenced win-back engine across DV360 and The Trade Desk that turns dormant users into active bookers through progressive cross-channel engagement -- paying CPM for awareness, CPC for consideration, CPA for conversion.

Dormancy segmentation and predictive scoring

We segmented users by dormancy duration, last booking value, historical travel preferences and engagement recency. A predictive reactivation score prioritized budget toward the segments with the highest win-back probability -- focusing 60% of spend on the top two deciles.

Sequenced cross-channel activation

We structured the campaign in a strict sequence: CPM display banners via DV360 for initial recall, CPC social ads via The Trade Desk for deeper engagement, personalized email offers for conversion, and push notifications for final urgency. Users progressed automatically based on their response to each stage.

Dynamic destination-based creatives

We personalized ad creatives with destinations and deals matched to each user's past search and booking history. Seasonal pricing, limited-time offers and countdown timers created urgency, driving a 2.6x higher click-through rate versus generic creatives.

Real-time engagement scoring

Every interaction -- ad view, click, email open, site visit -- fed a real-time engagement score that determined when a user was ready for the next channel in the sequence. This prevented overexposure on cheap CPM impressions and ensured higher-cost CPC and CPA channels activated only for qualified users.

Discuss your goals

Why Kalithea delivered the difference

Independent cross-channel orchestration

As an independent agency, we unified DV360, The Trade Desk, email and push into a single workflow with shared audience states. No platform conflicts, no walled-garden bias -- just the right channel for each user at each stage.

Multi-touch reactivation attribution

We built multi-touch attribution models that tracked the contribution of each channel in the re-engagement sequence. This gave the OTA clear evidence of which touchpoints drove incremental reactivations versus those that merely assisted -- enabling smarter budget allocation for future cycles.

Cost efficiency through intelligent sequencing

By reserving higher-cost CPC and CPA channels only for users who first responded to low-cost CPM display impressions, we reduced cost per reactivation by 52% compared to the OTA's previous single-channel approach. Every euro was spent in the right order.