MailChimp Option

More Info: https://docs.oceanwp.org/article/520-get-your-mailchimp-api-key-and-list-id

For API Key: https://mailchimp.com/help/about-api-keys/#API_key_security

For List ID: https://mailchimp.com/help/find-audience-id/

Creating API Key and List ID

Get API Key:

1. Login to your MailChimp account.

2. Under the user menu dropdown at the top left side, click on Account link.

Under the Your API keys section, create an API Key by clicking on Create A Key button. Once generated, copy API key for later use in PHP script.

Get List ID:

1. Choose a list in which all the subscriber’s information would be stored. In that case, you need to create a list in the Lists page.

Enter into your created list and navigate to Settings » List name and campaign defaults.

List ID

Some Plugin and integrations May request your List ID
Typically, This is What they want

Then, you just need to click on Theme Panel, and the Integrations tab to add your API and List ID.