Shared space between CRM and Exchange

Good Day,

We purchased Exchange on the cloud (50gig) and later on we also went to CRM now the CRM is talking to the Exchange server so that CRM can get the mail but the mail in CRM is in CRM and does not share the space on the Exchange so we have to purchase extra space in CRM to house any mail that we are tracking.

What I would like to know is the following

Is there a way (perhaps I am missing something) to utilize the space on the Exchange side instead of utilize the space on the CRM side.  the way it is setup now or it appears is that if we have a client who sends us mail, the mail not only resides on the Exchange but also in the CRM.

Thanks

Adam Raff