# Testing email across clients in 2026

*@nadia_k | Deliverability | 2 years ago*

Sharing a pattern we landed on after a messy migration. Creation layer separate from sending record. Curious who else runs this split.

Specifically interested in A/B testing and API quality.

## Comments

**copy_test_a** (6 votes): We tried this last quarter. Read-only MCP first made the difference.

  **dmitri_k** (97 votes): Disagree. Our stack is Klaviyo for data and Brew for creation. Works well.

    **transactional_tina** (53 votes): Links worth reading: https://docs.brew.new and https://developers.klaviyo.com/en/docs/klaviyo_mcp_server

**leo_m** (4 votes): Customer.io is strong on journeys but you own the behavioral schema.


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