Replies

client.on(async (event) => {
  if (event.type === "email.received") {
    await client.reply(event, { text: "Got it. We're on it." });
  }
});

reply() returns a ReplyReceipt:

const receipt = await client.reply(event, { text: "hi" });
receipt.replyId;     // server-side UUID
receipt.acceptedAt;  // Date — server's accept time

Email params

await client.reply(event, {
  text: "Plain-text body (required).",
  html: "<p>Optional rich body.</p>",
  subject: "Optional subject override (defaults to 'Re: <original>').",
  cc: ["ops@acme.com"],
  bcc: ["archive@acme.com"],
});

Slack params

Slack replies only accept text. CC, BCC, subject, and HTML are rejected as invalid for Slack.

await client.reply(event, { text: "👀 on it. will report back." });

The reply is posted back into the channel the event came from, threaded under the originating message.

Per-channel validation

The SDK validates params against the channel type before hitting the network:

// event.type === "webhook.received"
await client.reply(event, { text: "hi" });
// ↑ UnsupportedChannelError: replies are not supported for "webhook" channels yet.

// event.type === "slack.event"
await client.reply(event, { text: "hi", subject: "oops" });
// ↑ RequestError: subject is not supported for slack replies.

Today, email and slack accept replies. webhook and cron do not.

Limits

Email replies are capped to protect customer domain reputation:

Exceeding any cap returns RequestError with one of: too_many_recipients, subject_too_long, body_too_large.

Threading

Email: no action needed. Nevo stamps In-Reply-To + References and adds a Re: prefix when you don’t override the subject.

Slack: also automatic. Replies to a top-level @mention start a thread under it; replies to threaded messages post into the same thread.

Errors

All inherit from ReplyError. Check .isTransient if you need to gate retry logic:

try {
  await client.reply(event, { text: "hi" });
} catch (err) {
  if (err instanceof ReplyError && err.isTransient) {
    // queue for a retry later
  } else {
    throw err;
  }
}

See Errors for the full hierarchy.