Usage of 'Hi' and 'Dear' in Formal Communication [closed]

Solution 1:

You could start your first mail or two with "Hello [name]" and then switch to "Hi [name]" in future mails once you have established some rapport with the person. If you're in an environment where informal exchanges are encouraged, then you could start with "Hi [name]" in your communications.

"Dear Sir" or "Dear Madam" is always for formal communication where you do not intend to get to know the person well or cannot really form a personal rapport with the person (like for example, in the case of you being a service provider, say a bank, and addressing a customer or maybe you're in HR and are addressing an employee).

For addressing juniors, you could use "Hello" if you wish to be formal or "Hi" for informal communication.

Solution 2:

Hi is informal and Dear . . .. is formal, but Sir is formal and Junior is informal. It follows that Hi Sir and Dear Junior are mismatched. (I have to qualify that by saying that I can’t imagine anyone addressing anyone else in writing as Junior, but that is perhaps because it’s not used in British English.)