hi timo,
the problem is a missing mail server config.
Try setting one up as described here: How do I set up a mailbox for outbound documents?
Then create a routing as described here:
https://docs.metasfresh.org/webui_collection/EN/Setup_email_server_routing
BUT: instead of configuring the routing for a document or Process you select “Custom Type”:
Might be that you need a server cache reset to make it effective.
Let me know if that worked for you!
Norbert