Receiving and sending email through K2

Hi All, we are developing an application for a client (CMS) and one of the requirements is to be able to send and receive emails through the K2 Application. Sending emails is not an issue. I am not sure how to go about receiving emails in the K2 App. My idea was to use the subject to put some identifier (case ID ) to be able to figure out the link between the email and the case. I am not sure how I can retrieve and how to work with the emails. I don't have much experience in such integration. If anyone can help maybe. Thanks