I was answering emails and it got me to thinking about how I respond to different people. I do what I call 'reflective writing.' This method can be used with agents, editors, etc. Some people want to keep it strictly professional. They want you to use their title with last name and others are okay with you calling them by their first name, so I let the other person set the restrictions on our correspondence.
I always send a professional business query the first time, starting with Dear Mr. (insert name here) or Ms. (insert name). My queries end with Sincerely and my full name. Then I reflect back to them whatever style they choose to use. For instance, I have had some emails that start with Hey, K.C. and end with Thanks or Best Wishes. When I respond, I use their first name and end with the same closing. Get it?
My agent at Trident was an extremely excited individual. She used lost of exclamation points like Have a great day! or I loved the book! So when I wrote to her, I would put stuff like Have a great weekend!
I feel kind of silly doing this, but it seems to work. I've never had any complaints anyway. One time I sat in on a business seminar, and the guy running things told us to do this in person with people. If they are all business, you are all business. If they call you by your first name and joke around with you, then it's okay to do it back (as long as they aren't your boss). So I figured this would also work when writing to professionals. Anyway, thought I'd share that with you. Happy writing!