> For the complete documentation index, see [llms.txt](https://wiki.4thtech.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://wiki.4thtech.io/sdk/ethereum/mail/onnew.md).

# onNew

Sets up a listener for the event when a new mail is sent.

### Usage

```ts
const receiver = '0x...';
const sender = '0x...';

// Listen to received mails
mail.onNew(null, receiver, (envelope) => {
  console.log(envelope);
});

// Listen to sent mails
mail.onNew(sender, null, (envelope) => {
  console.log(envelope);
});

// Listen to all mails
mail.onNew(null, null, (envelope) => {
  console.log(envelope);
});
```

#### Stop watching

```ts
// Listen to received mails
const stopWatching = mail.onNew(null, receiver, (envelope) => {
  console.log(envelope);
});

// ... Later, to stop watching for the events
stopWatching();
```

### Returns

`UnwatchFn`

A function that can be invoked to stop watching for new event logs.

### Parameters

#### sender

* **Type** `Address | null`

The mail sender's address. If set to null, it listens for mails from any sender.

#### receiver

* **Type** `Address | null`

The mail receiver's address. If set to null, it listens for mails to any receiver.

#### callback

* **Type** `(envelope: ReceivedEnvelope) => void`

The callback function to be executed when a new mail event is detected. It receives a ReceivedEnvelope as its only argument.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://wiki.4thtech.io/sdk/ethereum/mail/onnew.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.