# Connect Reverse ETL Source to Bing Ads Audience


This guide takes you through the steps to connect a Reverse ETL source to the Bing Ads Audience destination.

## Set up the connection 

{{< warning >}}
**The Reverse ETL feature supports only source-driven pipeline configuration.**

Make sure you have [set up a RETL source]({{< ref "sources/reverse-etl/_index.md" >}}) and connected it to your Bing Ads destination before following the below steps.
{{< /warning >}}

1. [Confirm the connection settings]({{< ref "destinations/reverse-etl-destinations/bing-ads-audience/setup-guide.md#connection-settings" >}}) for Bing Ads Audience and click **Continue**.
2. In the [Data Mapping]({{< ref "data-pipelines/reverse-etl/developer-guides/visual-data-mapper.md" >}}) section, select the **Object** in the **Where do you want to sync data to?** section.
3. Set the [Sync mode]({{< ref "data-pipelines/reverse-etl/developer-guides/sync-modes.md" >}}) to specify how RudderStack should sync the data to Bing Ads.
4. In **Choose identifier**, specify the warehouse column that RudderStack uses to identify your records.
5. Map your warehouse columns to specific Bing Ads fields using the **Map fields** setting.

{{< image src="images/event-stream-destinations/bingads-identifier-map-fields.webp" >}}

## `audienceList` event structure

You can add or remove users from an audience by sending the `audienceList` call to Bing Ads.

```json
{
  "anonymousId": "2234232hK4el9Z",
  "channel": "sources",
  "properties": {
    "listData": {
      "add": [{
          "email": "alex@example.com"
        },
        {
          "email": "julie@example.com"
        },
        {
          "email": "peter@example.com"
        },
        {
          "email": "russell@example.com"
        },
        {
          "email": "john@example.com"
        }
      ],
    }
  },
  "type": "audienceList",
  "userId": "1hKOmRA4el9Z"
}
```

RudderStack maps the following properties to Bing Ads properties:

| RudderStack property | Data type | Bing Ads property | 
| :---- | :------ |:------|
| `properties.listData.add[i].email` <br/> <span style="color: #4D4DFF;font-size:12px;">Required</span>  | String | `email` |
| `properties.listData.remove[i].email` <br/> <span style="color: #4D4DFF;font-size:12px;">Required</span>  | String | `email` |

## FAQ

#### Why can't I add a Reverse ETL source from the destination page?

The Reverse ETL feature supports only source-driven pipeline configuration. It means that you must configure a Reverse ETL source in RudderStack and then connect it to a new or existing destination. Note that this destination should not be connected to any other source.

See [Reverse ETL FAQ]({{< ref "data-pipelines/reverse-etl/developer-guides/faq.md" >}}) for more information.