A great way to introduce yourself and gain the respect of the students is to post a short biography of your academic and professional background. The students can do the same to introduce themselves to the instructor.
I'm not sure why the instructor needs to send a welcome message to each individual student. The instructor in the classroom on site does not have an initial conversation with each student. She introduces herself to the class as a whole and has individual conversations on an as needed basis throughout the course. Why not do the same in the online environment?
