We're currently testing FME Server 2018.0 - Build 18265 - win64, and upgrade every transformer in Workbench before publishing. Because of some Python functionality that require Python 3.4+ or newer, we set 3.6 in all workspaces under 'Translation parameters'. Everything works fine on desktop. On server, however, the Emailer fails with message:
Python Exception <ModuleNotFoundError>: No module named '_socket'
PythonFactory failed to load python symbol `Emailer.Emailer'
Factory proxy not initialized
Most other transformers work well on server with 3.6+ set in the workspace, but in order to get Emailer to work, we have to switch back to 2.7.