Follow one email workflow
Provider
Postmark
Resend
Workload
Single send
2-person batch
5-person batch
The arrows are chronological from top to bottom. Dashed arrows are responses.
Codex agent
GPT-5.6
Email MCP
Postmark or Resend
Email provider
Postmark or Resend
Eval harness
fact-checks later
1. Send requested email(s)
2. Provider API send request
3. Accepted canonical ID(s) returned
4. MCP returns accepted ID(s) to Codex
5. Look up the same ID(s)
6. Provider-record lookup
7. Record(s) or temporary unavailable result
8. MCP returns lookup result to Codex
9. Final JSON with recipient, canonical ID, and observed state
10. Direct provider REST API fact-check
11. Canonical stored record
Select a stage
Send request
Trace evidence
Provider record
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