When to use last name and first name in an email?
Here is an example:
To someone who graduated from my school say 2 or 3 years ago. I sent him an email inquiring about an internship using the formal Mr. Smith. In his reply he was very friendly and signed as John. (say it's John Smith) I began my response with Dear John, but now that I think about I probably should have continued to use Mr. Smith.
So my question:
1. Should I have continued to use Mr. Smith?
2. When is it appropriate to write an email using first name?
3. John Smith was 2 years older, but should I use last name with someone who is the same age?