CRM 2011: workflow to create case: how to avoid new cases and get email body?

Hello all,

I have CRM 2011 on premises, with email router for a "support" email account, that as a queue in CRM.

With this i can get all the emails sent to support in CRM queue.

I also have a workflow that creates a case when a new email sent to this queue is created in CRM.

All of this is working fine.

My 2 questions are:

1) With this every single time a new email arrives to support queue a new case will be created; however, the customer maybe only repplying to an email sent, meaning, the case can already exists...

Any ideas on how can i check, for each email that arrives in that queue , if there is an already created case?

2) Also i don´t seem to be able to get the email body from the create case step in workflow...

Any ideas if this is possible? (i want to get the email body in a custom filed in my cases)

Thanks in advance.