Can confirm, I communicate via email with people from all over the world for work and typically use first/given name in the email salutation. Japanese names are easy to recognize first and last, as are the more common Korean last names like Park or Kim. Vietnamese on the other hand is often tough for me to discern first name. There's no typical convention by country in terms of name order in email addresses. It seems to be based on whether the company is more traditional/formal or not.