What email marketing plugin functionality (from any platform) maps to Klaviyo, Attentive, or Postscript on Shopify, and what's typically lost in translation?
Email platform migrations carry contacts, suppression lists and templates; flow logic, segment definitions and send history do not come across, and every automation gets rebuilt in the new tool (per Klaviyo's migration guide, September 2026). Klaviyo starts at $20 per month for 251 to 500 contacts; Attentive and Postscript are free to install with usage billed separately.
The honest inventory
| Asset | Moves? | How |
|---|---|---|
| Contacts and subscriber lists | Yes | Built-in sync from Mailchimp, Campaign Monitor, Constant Contact and Mad Mimi; CSV otherwise (per Klaviyo, Sep 2026) |
| Bounces and unsubscribes | Yes, manually | "Ensure any lists of bounces/unsubscribes are uploaded directly to your suppression list" (same source) |
| Email templates | Yes, with work | Klaviyo documents a transfer guide (same source) |
| Autoresponders and flows | No | "Migrate any existing autoresponders to flows and turn them live" means rebuild (same source) |
| Segment definitions | No | Re-authored against the new data model |
| Send and open history | No | Stays in the old platform |
| Signup forms | No | Swapped to point at the new provider (same source) |
The three rows in the middle are where the schedule goes. A mid-market program with fifteen live flows, each with branching and A/B splits, is several weeks of authoring and QA, not an import.
Why segments are harder than they look
A segment is a query against a data model. The legacy platform's model and Klaviyo's Shopify-native model do not hold the same fields, so "purchased in the last 90 days and opened twice" cannot be copied; it has to be re-expressed, and then it has to be checked against a population you can recognize. Do that check before launch by comparing counts: if your VIP segment was 4,200 people and the rebuilt one returns 6,800, the definition drifted.
And because open and send history does not migrate, any segment built on engagement starts empty and fills over weeks. Plan the first month's sends around purchase behavior, which does migrate through the Shopify integration, rather than engagement, which does not.
The three destinations
| Klaviyo | Attentive | Postscript | |
|---|---|---|---|
| Listing | apps.shopify.com/klaviyo-email-marketing | apps.shopify.com/attentive | apps.shopify.com/postscript-sms-marketing |
| Shape | Email, SMS and WhatsApp in one platform | Email and SMS, AI-led, with in-house TCPA compliance support stated on the listing | SMS-first, Shopify-only |
| Entry price | Free to 250 contacts; $20/mo for 251 to 500; SMS $15/mo for 1,250 credits | Free to install, charges billed separately | Free to install, charges billed separately |
| App Store standing | 4.7★, 3,294 reviews | 4.7★, 112 reviews | 4.7★, 1,145 reviews |
Verified on the live listings, September 2026. Attentive's and Postscript's real pricing is contract-based and not published on the listing; treat the free-to-install line as an installation fact, not a cost.
The verdict, with the profile
Klaviyo is the default for a $20M to $500M merchant consolidating email and SMS into one place, and the reason is the Shopify data model rather than the feature list: segments built on order behavior work on day one because the integration is native and real-time.
Attentive suits a brand where SMS is the primary revenue channel and the team wants managed support, including the compliance help its listing advertises. Postscript suits a Shopify-only brand that wants an SMS specialist and is willing to run email elsewhere.
The combination to avoid is two vendors with overlapping consent capture and no agreed source of truth for subscription status. That is how a customer receives the same promotion twice and unsubscribes from both.
What to do about deliverability
Sending reputation attaches to the sending domain and IP, not to the platform. Moving platforms with the same authenticated domain preserves domain reputation; moving onto shared or new IPs resets the IP side. Warm up by sending the first campaigns to your most engaged segment, which you will have to approximate from purchase recency because the engagement history stayed behind. This is the strongest argument for running both platforms in parallel for two weeks rather than cutting over on a Friday.
The Deploi point of view
Our own position, from building on Shopify. Separate from the facts above.
- Our take: Rebuild the flows you can defend and delete the rest. A migration is the only moment a team will honestly audit fifteen automations, and in our experience about a third of them are running on assumptions nobody has revisited since they were built.
- What we’ve seen: The engagement-history gap is the underestimated one. Teams plan for the flow rebuild and then discover their entire segmentation strategy depends on data that did not come.
- Where we disagree: Vendor migration services are sold as full-service and are mostly contact and template work. The flow logic is yours either way, and outsourcing it hands your retention strategy to whoever is cheapest on the statement of work.
- What this page adds: the asset-by-asset inventory of what actually transfers between email platforms, and why engagement-based segments start empty.
Reviewed by Martin Dejnicki, Director of SEO & AI Search. Facts verified 2026-09-13.