WS2K12R2 (Standart edition) whether it is possible to lift a role of a mail server if it already carries out a role of a terminal server?

Question

Mail server

There is a WS2K12R2 server (Standart edition), the Hyper-V role is raised on it. Raised 2 VMs also WS2K12R2 (Standart edition).
1 VMs - the role of AD and DNS.
2 VMs - role TS(Remote Desktop Services) and IIs.
The problem is that this edition has Virtualization rights for 2 VMs. And I need to lift still a role of the e-mail server.
I wanted to raise this role to TS, but I'm afraid this is fundamentally wrong. Tell me how to do it better. I hope for your advice. Thank you!