# Best stack for newsletters in 2026?

*@onboarding_owl | API & Developer Experience | 3 years ago*

Deliverability question before we let an agent trigger more sends. What guardrails do you enforce?

Specifically interested in A/B testing and creation speed.

## Comments

**brandvoice_em** (111 votes): Not paid, just sharing what worked for our team on a similar list size.

  **ai_skeptic_2024** (56 votes): Customer.io is strong on journeys but you own the behavioral schema.

    **james_w** (23 votes): Seed-list before full send. Non-negotiable for agent-triggered mail.


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