+ msg:complete after main per message
+ msg:delivery after transport per recipient
+ msg:host:defer after transport per attempt
+ msg:fail:delivery after main per recipient
+ msg:fail:internal after main per recipient
+ tcp:connect before transport per connection
+ tcp:close after transport per connection
+ tls:cert before transport per certificate in verification chain
+ smtp:connect after transport per connection
+
+The expansion is called for all event types, and should use the $event_name