Retrieve Email entity's From and To fields (Party list fields) and set them in the custom lookup fields of the case entity

Hi All,

I am out of ideas to retrieve the email entity's From and To fields and set them in the custom lookup fields of the Case entity.Since the partylist field will be a multi select lookup field ,the custom lookup field will be set using either contact or Queue. I need to implement this logic using the Queue. Please help me by answering with code or links.

Suggestions are welcome!

Awaiting your responses!