Hi ,

we have plan to install 2013 exchange server . and we have one  enterprise edition licences.

For installation i have plan to install CAS and Mailbox roles in separate server.

1.For one enterprise license we can use both CAS server system and Mailbox server system.

It will work (one single license )  ? or we need to purchase separate one more enterprise license ?

if we use same license in cas and mailbox server any issues will

Please refer below link. it may heal you in this case. 

https://www.directionsonmicrosoft.com/licensing/2013/02/exchange-2013-packaging-pricing-and-licensing

Hi,

Exchange is licensed by instance and each instance, regardless of role, needs a license. You can install Mailbox Server and Client Access Server on same server by one license. But you can't use it twice.

Best Regards.