email.replied

Fires together with email.received, for every message from outside the workspace that arrives in a connected mailbox in a thread that is a conversation.

Despite the name, this is not limited to replies. The first message of a new thread fires it too, and the payload is identical to email.received’s, messageId included. A subscription to both events handles every incoming message twice.

Payload

{
  "id": "whd_9Lm3qT7vR",
  "event": "email.replied",
  "createdAt": "2026-09-11T14:02:37.121Z",
  "data": {
    "messageId": "18f2d3e7a9b1c4f6",
    "threadId": "18f2d1c04b7e9a23",
    "channelId": "chan_4Kp8wN",
    "conversationId": "conv_3Hq9rT",
    "from": "ada@ravennafoods.com",
    "fromName": "Ada Lovell",
    "to": ["sales@acme.com"],
    "cc": [],
    "subject": "Re: Pricing for the Ravenna rollout",
    "receivedAt": "2026-09-11T14:02:31.000Z",
    "folder": "INBOX"
  }
}

string

required

The mail provider’s id for the message. The same value the matching email.received carries. Always present.

string

The mail provider’s id for the thread.

string

The connected mailbox the message arrived in.

string

The conversation the thread belongs to. Present on every delivery.

string

The sender’s address.

string

The sender’s display name. Omitted when the message carries none.

string[]

The addresses the message was sent to.

string[]

The addresses copied. An empty array when nobody was copied.

string

The subject line. An empty string when the message has none.

string

The message’s date, as an ISO 8601 timestamp.

string

The provider’s id for the first folder or label the message is filed under. Omitted when the provider lists none.

string[]

Records the message is linked to. Mail from a connected mailbox does not carry them today, so this is omitted.

When it fires

Exactly when email.received does: the sender is outside the workspace, the message is not filed as spam, and the thread is a conversation. The email.received page lists what sends nothing.

Telling a reply from a first message

The payload does not say which one a message is. To act only on replies, keep the conversationId of every email.received or email.replied and every email.sent you handle: a message whose conversation you have already seen continues a thread you know about. A conversation that began before your endpoint subscribed reads as new the first time it appears.

Example

custral.on("email.replied", async (event) => {
  const {conversationId, from, subject} = event.data;

  // Every incoming message fires this, the first one in a thread included.
  const key = `conversation:${conversationId}`;
  const seenBefore = await store.has(key);
  await store.add(key);
  if (!seenBefore) return;

  await followUps.markAnswered({conversationId, from, subject});
});

Getting started

Building a receiver

Event reference

Operations

Payload

When it fires

Telling a reply from a first message

Example

​Payload

​When it fires

​Telling a reply from a first message

​Example

Payload

When it fires

Telling a reply from a first message

Example