Workflow 2.0 in GP 2013 R2 is pretty cool but it is a first release so it’s not perfect. Checkout GP 2013 R2: Workflow 2.0 – Email Messages Setup Error for something to look out for.
GP 2013 R2: Workflow 2.0 – Email Messages Setup Error – Microsoft Dynamics GP Community
Install, Upgrade & AdminGP 2013
Archived post from 2014. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.