If it's just a general question or comment to an unknown person, i.e. firstname.lastname@example.org
, just start with something simple like:
Greetings!, Good morning!, Good afternoon!, Hello!
Keep the message short and to the point. People are busy and don't have time to read your life story, as a general e-mail box like this probably receives 100+ messages a day.
If you are writing someone with a name, i.e. the Dean of Admissions or a known staff person, then address the message:
Dear Dean xxxx, Dr. xxxx or Mr./Mrs./Ms. xxxx
End the message with a simple "thank you" or "thanks for your assistance" and your name, phone #, e-mail address and/or USPS mailing address, as is appropriate.
The bottom line is, keep everything short and simple!