CRM online email to case

Hi guys,

I have created an email to case in my organisation's CRM. So whenever someone send to the queue, a case will be created.

I also have a plugin for the Pre-Validation pipeline, Message: Create, Primary Entity: incident.

I would like to know in this case how do I debug the plugin:

Let's say when an incoming email is sent to the queue, before a case get created, the pre-validate plugin will fire, how do I debug this plugin before the case get created?

Thanks.