The salutation you use in an email matters.
A salutation is the first thing most people read, it sets the tone for the rest of the email, and it demonstrates your level of professionalism. For good or bad, it also carries the power to influence your reader. And you don’t want the person who reads your email to be annoyed or offended right from the start—especially if your plan is to ask a favor.
When you send an email to a friend, “Hi,” or “Hey,” or “Yo” or (even nothing) is a perfectly acceptable salutation. But when you email a professor, instructor, teaching assistant, or campus administrator you should use a formal approach and include the professional tittle of the person you email. Fortunately, it’s easy to do and only takes a few seconds.
For example, if you’re emailing a professor about a research position, an override for a full class, or a letter of recommendation start your email with “Dear Dr. X” or "Dear Professor X." If you’re not sure of the correct title, search the online college directory to find it or opt for “Dear First Name Last Name.” However, most won’t be offended if you use “Dr.” regardless of the degree they hold. What you should never, never use is “Miss,” or “Mr.” or “Mrs.” unless you’ve been instructed to do so from the person you are emailing.
Once you’ve established an informal or mentoring relationship with someone, you’ll likely be instructed to drop the title but until (and unless) you’ve received that golden ticket, keep your emails formal to remain professional.
When you use a formal approach, those who care about the salutation will be more open to the favor you’re asking, and those who don’t care won’t be offended by your elevated level of professionalism.
On its own, an email salutation won’t get you a letter of recommendation, or a research position, but it might help set the stage and it won’t irk someone just before you ask for a favor.
Professionalism is all about the details.