# What is ESP – Email Service Provider?

What is ESP – Email Service Provider? A platform for sending marketing emails. Klaviyo, Mailchimp, Omnisend.

## How it works in practice

An ESP that doesn't sync with Shopify/WooCommerce means lost data and non-functioning automations.

## Related metrics

- Email Marketing — the ESP is the tool
- Segmentation — segmentation capability depends on the ESP
- Automation — flow logic depends on the ESP
- Deliverability — a good ESP means good deliverability

## Common misconception

'Free Mailchimp is enough.' Free Mailchimp doesn't offer deep integration with Shopify, predictive CLV, or forecasted CLV.

## How to fix it

ESP not working? (1) is the store integration functioning? (2) deliverability — check mail-tester.com, (3) are flows active?

## Real-world example

A clothing store switched from Mailchimp to Klaviyo. Email revenue went from 12% to 27% of total revenue within 3 months.

## Where to start

Klaviyo is free up to 1,000 subscribers. Above that: $45/month.

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Category: Marketing · From the [Jimmy OS KPI Glossary](https://jimmy-os.com/glossary/kpi.md) · Source page: https://jimmy-os.com/glossary/kpi/esp-email-service-provider