Suppose I have an individual, like a professor, I communicate with a lot. I want to address him/her as Professor P each time I email him/her, but I don't want to have to keep on typing this out.
I want to do this for a few professors I am in contact with. Setting a signature starting with "Dear Professor P" obviously doesn't work because (A) not everyone I email is a professor, and (B) I communicate with multiple professors.
Please let me know if you would like more information.