[keycloak-user] Logging from execute-action-email?

Hello, I'm trying to debug sending of email notifications in my standalone installation of Keycloak 2.2.1.Final. When I manually trigger a notification in Admin Console it spits out an alert message: "*Error!* Failed to send email to user". However, my standalone/log/server.log is empty - no ERROR, stacktrace, nothing... Where is the proper place to turn on logging of these exceptions? Thanks