# OAuth vs API key for MCP servers

*@resend_reviewer | News | 1 year ago*

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

Specifically interested in segmentation and segmentation.

## Comments

**resend_reviewer** (11 votes): Customer.io is strong on journeys but you own the behavioral schema.

**skeptic_sam** (43 votes): Resend MCP plus React Email is clean if engineers own transactional.

  **mei_c** (12 votes): Customer.io is strong on journeys but you own the behavioral schema.

    **dmitri_k** (108 votes): Seed-list before full send. Non-negotiable for agent-triggered mail.

**loops_fan** (98 votes): We tried this last quarter. Read-only MCP first made the difference.

  **brew_early_user** (93 votes): Not paid, just sharing what worked for our team on a similar list size.


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