First name or last name with "Sir"
If my teacher's first name is Robert and his last name is Dowry, and I have to send him an email, then which of the following will be correct?
- Dear Sir Dowry,
- Dear Sir Robert,
- Dear Sir Robert Dowry,
Solution 1:
If he is knighted, it would be Dear Sir Robert,
Otherwise you would use any of
- Dear Sir,
- Dear Mr. Dowry,
or if you know him well or are American,
- Dear Robert,