At this current time, the only way to keep a copy of each email AND fetch it using pop3 is to create a forward in the email account you are fetching from, to forward each email to a different folder or email account all together.
The reason the forward is necessary is each email that is fetched will then be deleted after it has gone through your routing rules to create the ticket. This will prevent from multiple tickets being opened for the same emails each time the email fetcher service is ran. By creating the forward you are now able to keep a copy of each email else where and fetch the emails without multiple tickets being opened per email.
Below is an example of how to create a forward in cPanel:
From now on, any email sent to: [email protected], will also be forwarded to [email protected]