While a simple "Hi," "Hello," or even "Hey" is appropriate in casual correspondence, a more formal salutation is appropriate when you are emailing about a business_related matter, such as a cover letter, letter of recommendation, or inquiry letter.
Do you need to write a business letter? Not sure about the best layout to use or what to include in your letter? It's important that all the business letters you write are properly formatted and professional in appearance. When you are writing to prospective employers, colleagues, professional and business connections, the layout of your letter is almost as important as what you are writing. If the letter isn't formatted correctly, doesn't have enough space between paragraphs, and uses a non_traditional font style or size, it can reflect poorly on you.