I am one of those people that believe that an email should treated similar as if you were to write an actual pen and paper letter. The only difference is the email is quicker, and easier to address. With that in mind, writing a single sentence, and expecting me to reply is likely not going to happen. Even in long term relationships, I try to write back in kind.
So, what would I want in an initial email? Well, what would you write to a new person that you are writing a letter to? How about tell me a little about yourself. Tell me about the work you do, and the things that interest you. Tell me about the music, TV shows, and movies you enjoy. Maybe tell me a little about where you live. How about any pets you may have, or family you keep in touch with.
Now, you do not have to tell me these things, but you should write at the very least a couple of paragraphs (usually 3-5 sentences in a paragraph). I would not recommend that you tell me very personal information such as birthdate, government ID numbers, or bank account information. In addition, I will not ask for this information, nor will I give such information out to someone.