such definition of an element states that it could be null or even omitted.
As far I could observe error occure on parsing of message somewhere in the middle of the weblogic handlers chain (however there is no any non-standard handlers for all webservices) and before my webservice implementation is invoked, but I'm not sure what is the root cause and how to fix the situation and let null values to be passed.
this one is the exception thrown,
I just can't find out what does it mean - 'can't have mixed content'.
Below are the full logs of call with email set to null: