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Lettr

Choose Lettr immediate or scheduled submission and preserve count-only outcomes.

Import lettrEmailLayer from @corven/email-sdk/lettr to provide the common Email service for this account.

Configure the account

import { Layer } from "effect";
import type { Redacted } from "effect";
import { lettrEmailLayer } from "@corven/email-sdk/lettr";
import { emailHttpLayer } from "./sending.js";

export const configuredLettrAccount = (apiKey: Redacted.Redacted) =>
  lettrEmailLayer({ apiKey, submissionMode: "Immediate" }).pipe(Layer.provide(emailHttpLayer));

The example reuses the explicit HTTP Layer. Acquire credentials in trusted host code, then provide this account Layer to your sending program.

Message behavior

  • Use a live lttr_ credential. Sandbox recipient rewriting is not supported.
  • Immediate and Scheduled are different configured modes. Scheduled mode enables scheduling and requires the scheduled acknowledgment shape.
  • Attachments require explicit MIME types. Inline attachments are unsupported; one tag and common metadata are available.
  • Acceptance/rejection counts do not identify which recipients belong to each group. Preserve count-only receipts.

Idempotency

Immediate mode declares native 24-hour replay using keys up to 255 characters containing only letters, digits, dots, underscores or hyphens. Scheduled mode declares no send key support.

Read field support before switching accounts, and receipts and retries before adding recovery behavior. Configuration and local validation do not authenticate the account or prove delivery.