We Migrated 47 Brands from Mailchimp to Klaviyo. Here's What Happened.

This isn't a "Klaviyo vs. Mailchimp" comparison post where we list features side by side and tell you to "choose the one that's right for your business." You can find a hundred of those on Google.

This is real data from 47 actual migrations we've done at GOSH Digital — Shopify brands that were on Mailchimp and moved to Klaviyo. What broke. What improved. How long it took. And most importantly, what happened to revenue.

We're Klaviyo Gold Partners, so yes — we're biased. But the numbers aren't. And the numbers are why we keep recommending this migration to every eCommerce brand still on Mailchimp.

The TL;DR (For People Who Scroll)

Across 47 migrations:

• Average revenue increase from email: 62% within 90 days
• Average time to complete migration: 2-3 weeks
• Biggest single improvement: Automated flow revenue (went from near-zero to 25-40% of total email revenue)
• Most common thing that broke: Nothing critical. Some template formatting issues.
• Would brands go back to Mailchimp? 0 out of 47.

Now let me break this down properly.

Why Brands Were on Mailchimp in the First Place

Most of the 47 brands ended up on Mailchimp for the same reasons:

1. It's what they heard of first
2. The free tier got them started
3. Their web developer set it up during the Shopify build
4. "It works fine" (it didn't, but they didn't know what they were missing)

And look — Mailchimp is fine for newsletters. If you're a blogger, a non-profit, or a local business sending a monthly update, Mailchimp does the job. We're not hating on it.

But for eCommerce? For Shopify brands trying to make email and SMS a real revenue channel? Mailchimp is a bicycle and Klaviyo is a car. They both have wheels. That's where the similarities end.

What Was Wrong With Their Mailchimp Accounts

Before migrating, here's what we typically found in these Mailchimp accounts:

Almost No Automation

Mailchimp has "Customer Journeys" (their version of flows), but they're limited. Most of the 47 brands had:

• A basic welcome email (1 email, no series)
• Maybe an abandoned cart email (again, 1 email)
• That's it. Two automated emails.

In Klaviyo, we typically build 12-20 automated flows per account. The automation gap was massive.

No Segmentation Beyond "All Subscribers"

Mailchimp has tags and segments, but the conditions are limited compared to Klaviyo. Most brands were sending every campaign to their entire list. No engagement-based targeting. No purchase behavior segmentation. Every subscriber got the same email.

No Revenue Attribution

Mailchimp shows you opens and clicks. Klaviyo shows you opens, clicks, and exactly how much revenue each email generated. Revenue attribution changes everything about how you make decisions. It's the difference between "that email had a 25% open rate" and "that email generated $4,200 in revenue."

Limited Shopify Integration

Mailchimp's Shopify integration has improved over the years (they famously broke up and got back together), but it's still not native the way Klaviyo's is. Klaviyo pulls in real-time purchase data, browse behavior, cart data, product catalog, customer lifetime value — all automatically. That data powers everything.

The Migration Process (What Actually Happens)

Here's exactly what we do when migrating a brand from Mailchimp to Klaviyo. This process has been refined over 47 migrations.

Week 1: Setup and Data Migration

Day 1-2: Account setup

• Create Klaviyo account and install the Shopify integration
• Set up dedicated sending domain (DKIM, SPF, DMARC)
• Configure SMS (if applicable)
• Import brand assets (logo, brand colors, fonts)

Day 3-4: Data migration

• Export all subscribers from Mailchimp (with engagement history, tags, and custom fields)
• Import into Klaviyo via CSV upload
• Map Mailchimp tags to Klaviyo properties
• Verify subscriber counts match

Day 5: Segment creation

• Build the 12 core segments (see our segmentation guide)
• Map old Mailchimp audience groups to Klaviyo segments
• Create suppression lists for unsubscribes and bounces

What can go wrong here: Not much. The data migration is straightforward. The main risk is losing subscriber engagement history. Mailchimp doesn't export "last opened date" in a way that maps cleanly to Klaviyo. We solve this by tagging imported subscribers with their last known engagement window (e.g., "Mailchimp Active 30d", "Mailchimp Active 90d", "Mailchimp Inactive 90d+") and using those tags for the first 90 days of sending.

Week 2: Flow Building

This is where the magic happens. And it's where Klaviyo blows Mailchimp out of the water.

Flows we build during migration:

1. Welcome Flow (5 emails)
2. Abandoned Cart Flow (4 emails + SMS)
3. Abandoned Checkout Flow (separate from cart — higher intent)
4. Browse Abandonment Flow (3 emails)
5. Post-Purchase Flow (4 emails)
6. Cross-Sell Flow (based on product category)
7. Replenishment Flow (for consumable products)
8. Win-Back Flow (3 emails)
9. Sunset Flow (2 emails → suppress)
10. VIP Exclusive Flow (triggered by entering VIP segment)
11. Price Drop Flow (triggered when a browsed product goes on sale)
12. Back in Stock Flow (triggered when an out-of-stock item is restocked)

Most of these flows don't exist in Mailchimp because the platform can't handle the behavioral triggers. Browse abandonment? Requires real-time Shopify browsing data that Mailchimp doesn't pull. Price drop alerts? Mailchimp doesn't monitor your product catalog for price changes. Back in stock? Same problem.

This is the single biggest revenue unlock in the migration. Brands go from 2 automated emails to 40+ working 24/7.

Week 3: Template Design and Campaign Migration

Template design:

• Build 3-4 campaign templates in Klaviyo's drag-and-drop editor matching the brand's look
• Build flow email templates (these are usually simpler — performance > aesthetics in flows)
• Test across email clients (Gmail, Apple Mail, Outlook, Yahoo) using Litmus or Email on Acid

Campaign migration:

• Recreate any recurring campaigns (monthly newsletter, weekly roundup)
• Set up campaign calendar
• Configure A/B testing defaults

What can go wrong here: Template formatting is the most common issue. Mailchimp templates don't transfer to Klaviyo. You have to rebuild them. It's annoying but not difficult. The bigger issue is when brands have complex Mailchimp templates with custom HTML — those need to be translated to Klaviyo's template language, which is different.

Week 3-4: Warm-Up and Go-Live

Since you're on a new sending domain, you need to warm up. See our deliverability guide for the full warm-up schedule.

During warm-up:

• Send to most engaged subscribers first
• Monitor inbox placement with GlockApps
• Check Google Postmaster Tools for domain reputation
• Gradually increase volume over 3-4 weeks

Important: Don't turn off Mailchimp immediately. During the warm-up period, we run Mailchimp and Klaviyo in parallel — Mailchimp handles the bulk of campaigns while Klaviyo warms up. Once Klaviyo is at full volume with good deliverability, we shut down Mailchimp.

The Results: What Actually Changed

Here's the aggregate data across 47 migrations. These numbers are measured 90 days post-migration compared to the 90 days prior.

Revenue from Email

| Metric | Mailchimp (Before) | Klaviyo (After 90 Days) | Change | |---|---|---|---| | Email as % of total revenue | 8-15% | 25-40% | +15-25 points | | Monthly email revenue (avg) | $12,400 | $20,100 | +62% | | Revenue from flows | $1,800 | $9,200 | +411% | | Revenue from campaigns | $10,600 | $10,900 | +3% |

Look at those numbers carefully. Campaign revenue barely changed. The massive jump came almost entirely from automated flows. That's 12-20 flows running 24/7 that simply didn't exist in Mailchimp.

Engagement Metrics

| Metric | Mailchimp | Klaviyo | Change | |---|---|---|---| | Average open rate | 19.2% | 31.4% | +64% | | Average click rate | 1.4% | 3.2% | +129% | | Unsubscribe rate | 0.35% | 0.12% | -66% | | Spam complaint rate | 0.04% | 0.008% | -80% |

Why did open rates jump 64%? Two reasons: segmentation (sending to engaged subscribers instead of the full list) and better subject line testing (Klaviyo's A/B testing is significantly more flexible than Mailchimp's).

Why did unsubscribes drop 66%? Because we stopped sending irrelevant emails to people who weren't interested. Segmentation isn't just a revenue play — it's a retention play.

SMS Impact (For Brands That Added SMS)

28 of the 47 brands added Klaviyo SMS during migration. Average results:

| Metric | Value | |---|---| | SMS list growth (first 90 days) | 8-15% of email list opted in | | SMS revenue as % of total email+SMS revenue | 12-18% | | Average revenue per SMS message | $0.15-$0.30 | | Average ROI on SMS spend | 25-40x |

SMS was a bonus — most brands coming from Mailchimp had never done SMS marketing. Adding it during migration means they start generating SMS revenue from day one.

What Breaks During Migration

Let's be honest about the downsides.

1. Template Rebuilds

Every template needs to be rebuilt from scratch. For brands with 10+ templates, this takes time. Budget 5-8 hours for template design.

2. Historical Data Limitations

Mailchimp doesn't export everything cleanly. You lose some historical campaign analytics. Klaviyo will have a "fresh start" for reporting — which means your year-over-year comparisons get messy for the first 12 months.

3. Warm-Up Period

The 3-4 week warm-up means you can't send at full volume immediately. During this period, your overall email revenue might temporarily dip because you're reaching fewer people. Every client we've migrated has seen revenue surpass pre-migration levels within 60 days.

4. Learning Curve

Klaviyo is more powerful than Mailchimp, which means it's more complex. If your team is used to Mailchimp's simple interface, expect a 1-2 week learning curve. Klaviyo's flow builder, segmentation engine, and analytics dashboard are different from anything in Mailchimp.

5. Price Increase

Let's address this directly. Klaviyo costs more than Mailchimp. For a 50,000-subscriber account:

• Mailchimp Standard: ~$350/month
• Klaviyo: ~$720/month

That's roughly 2x the cost. But if Klaviyo generates 62% more email revenue (our average), the ROI math isn't even close. A brand doing $12K/month in email revenue on Mailchimp pays $350 for the privilege. That same brand does $20K/month on Klaviyo and pays $720. The extra $370/month generates an extra $8,000/month in revenue. That's a 21x return on the incremental cost.

The Brands Where Migration Mattered Most

Pattern 1: The Consumable Product Brand

Brands selling supplements, food, coffee, skincare — anything that runs out. These brands saw the biggest revenue jumps because of Klaviyo's replenishment flows. Mailchimp can't trigger an email based on "it's been 30 days since they bought a 30-day supply of vitamins." Klaviyo can. Average additional revenue from replenishment flows alone: $2,000-$5,000/month.

Pattern 2: The Fashion/Apparel Brand

Browse abandonment was the game-changer here. Fashion shoppers browse a lot before buying. Mailchimp doesn't capture browse data from Shopify. Klaviyo does. A 3-email browse abandonment flow for fashion brands typically generates $1,500-$4,000/month in revenue that literally didn't exist before.

Pattern 3: The Brand With a Large But Dead List

Brands with 100K+ subscribers and 10% engagement. Mailchimp's limited segmentation meant they were blasting everyone and killing their deliverability. Moving to Klaviyo + implementing proper segmentation + running a sunset flow brought their deliverability back to life. Open rates went from 12% to 35% in 90 days.

The Brands Where It Mattered Less

Not every migration is life-changing. Brands with small lists (under 5,000 subscribers) and simple product lines don't see as dramatic a shift because:

• Flow revenue is proportional to traffic/list size — small lists generate less flow revenue
• Fewer products mean fewer cross-sell and browse abandonment opportunities
• The warm-up period hits harder when you're already sending to a small audience

For these brands, the migration still makes sense long-term (they'll grow into Klaviyo's features), but the 90-day impact is more like 20-30% revenue increase instead of 60%+.

How to Know If You Should Migrate

Migrate from Mailchimp to Klaviyo if:

• You're on Shopify (or any major eCommerce platform)
• Your email list is 5,000+ subscribers
• You want automated flows to generate revenue while you sleep
• You care about revenue attribution (not just open rates)
• You plan to add SMS marketing
• Your current email revenue is below 25% of total revenue

Stay on Mailchimp if:

• You're a blogger or content creator (not selling products)
• Your list is under 2,000 and budget is tight
• You only send newsletters (no automation needed)
• You don't sell on Shopify/WooCommerce/BigCommerce

Ready to Migrate?

We've done this 47 times. The process is documented, the risks are known, and the results are consistent. If you're on Mailchimp and want to know what Klaviyo could do for your revenue, we'll run a free audit on your current setup and project the expected impact.

Book your free migration consultation.

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Mark Cijo is the founder of GOSH Digital, a Klaviyo Gold Partner agency that's driven $23M+ in revenue for 150+ eCommerce brands. He's personally overseen 47 Mailchimp-to-Klaviyo migrations and has never had a client ask to go back.