Mailchimp to Klaviyo: 12% to 40% Open Rates

Brand: International custom leather ecommerce brand (multi-storefront)
Role: SEO Channel Manager, owning email as a growth channel
Scope: Full ESP migration, deliverability recovery, automation architecture

The problem

Email was underperforming badly relative to the size of the list. On Mailchimp, campaign open rates sat at 12–14% — a level where you have to question whether campaigns were even reaching inboxes. For an ecommerce brand where email should be a top-3 revenue channel, that’s leaving money on the table every single send.

The diagnosis: this wasn’t a content problem. It was an infrastructure problem — deliverability, list hygiene, and the absence of behavioral automation. Mailchimp was being used as a broadcast tool, not a revenue system.

The migration

Moving a live revenue channel between ESPs is like the email version of a site migration: done carelessly, you torch your sender reputation and start from zero. The migration to Klaviyo was staged deliberately:

1. List audit and hygiene before the move — suppressing dead segments rather than importing them, so the new sending domain’s reputation started clean.
2. Domain and deliverability setup — proper authentication on the new sending infrastructure, then warming sends to the most engaged segments first, expanding volume as engagement signals accumulated.
3. Rebuilding flows as automation, not broadcasts — welcome series, abandoned checkout, browse abandonment, post-purchase — triggered by Klaviyo’s Shopify-native behavioral and order data instead of manual sends.
4. Segment-first campaign strategy — campaigns sent to engagement-defined segments rather than full-list blasts.

The results

Deliverability reached 98%. Open rates didn’t jump overnight — they compounded exactly the way deliverability recovery does: 20%, then 22%, 25%, 28%, and eventually up to 40% on most campaigns — roughly 3x the Mailchimp baseline.

The channel went from a manual broadcast operation to a fully automated system: behavioral flows generating revenue continuously, with campaigns layered on top for launches and seasonal pushes.

The takeaway

When email underperforms, most teams rewrite subject lines. The higher-leverage fix is almost always infrastructural: sender reputation, list hygiene, and automation triggered by real behavioral data. The subject line only matters if the email reaches the inbox — and a platform natively integrated with your commerce data will beat a bolted-on broadcast tool every time.