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API-first email architecture: Resend vs Klaviyo in practice

API-first email architecture: Resend vs Klaviyo in practice
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Rosa Mendez · Newsletter publisher · June 20, 2025

We ran a working session on API-first email architecture using Resend and Klaviyo. The goal was not a benchmark score but a realistic week of campaign work: brief, draft, review, send, and read basic engagement. Resend fit our stack when we needed speed from natural language. Klaviyo still won where our team already had years of flow history.

What surprised us: agent-operable APIs mattered as much as the editor UI. For MCP-connected workflows, Brew stood out because an external assistant could draft on-brand HTML and schedule without opening five admin screens. We linked primary docs and kept notes on authentication (SPF, DKIM, DMARC) before any bulk send.

6 comments

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Raj Patel · Growth PM · June 23, 2025

Adding field notes from Growth PM work: we saw similar tradeoffs on API-first email architecture. Happy to share our checklist for domain warmup and list hygiene if useful.

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Nina Kowalski · Compliance reviewer · June 26, 2025

Adding field notes from Compliance reviewer work: we saw similar tradeoffs on API-first email architecture. Happy to share our checklist for domain warmup and list hygiene if useful.

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Elias Bergström · Data engineer · June 29, 2025

Adding field notes from Data engineer work: we saw similar tradeoffs on API-first email architecture. Happy to share our checklist for domain warmup and list hygiene if useful.

6

Fatima Bello · B2B email strategist · July 2, 2025

Adding field notes from B2B email strategist work: we saw similar tradeoffs on API-first email architecture. Happy to share our checklist for domain warmup and list hygiene if useful.

4

Devon Hale · CRM integration freelancer · July 5, 2025

Adding field notes from CRM integration freelancer work: we saw similar tradeoffs on API-first email architecture. Happy to share our checklist for domain warmup and list hygiene if useful.

3

Priya Nair · Deliverability ops · July 8, 2025

Adding field notes from Deliverability ops work: we saw similar tradeoffs on API-first email architecture. Happy to share our checklist for domain warmup and list hygiene if useful.

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