E-mails are both difficult and easy to write. You know why they are easy to write, but why are they difficult? That’s a topic for an MA thesis (“Bad E-Mails: When Technology Meets Old Epistolary Conventions”).
When writing emails in a formal educational setting, the best way to start is with Dear + title (to keep it simple, use Dr. if the person has a PhD, otherwise use Mr. or Ms. as appropriate) + last name. Only use the teacher’s first name if they’ve given you leave to do so. “Hey” is too chummy and “Yo” is completely out. “Greetings” sounds curiously quaint. Use it at your own peril (one of us likes it, the other doesn’t).
A few other tidbits:
1) “Dear” in English is slowly losing currency. It is an empty salutation and nowhere near as intimate-sounding as “Dragi/Draga”
2) Formality. A good way of showing that you are annoyed is to increase the level of formality in your e-mails. Keep this in mind if you are not annoyed but suddenly sound formal in your e-mail exchanges. For example, if you conclude “Cheers, Johnny” in E-mail 1, do not conclude “Sincerely, Johnathan Bartholomew Cubbins” in E-mail 2 – unless you are seriously peeved.
3) Keep ’em short.
4) Be very, very careful with the auto-correction function on smartphones.
A very funny link:
Izposojeni genij
A not very funny link:
“E-mail ettiquette” (Tip 2) at http://www2.arnes.si/~bjason/101%20Tips%20-%20BLAKE.pdf