As fdmaxey pointed out "Hi there" can be very personal. It is like saying "Hi, to you in particular". I suspect that the email is trying to make a personal connection with you by being very familiar. It is most likely a marketing trick. "Hi there" can also be used when you are trying to get someone's attention. You see someone in the next room and decide to say "Hi!" Hi! -you say. The person doesn't answer. Maybe he/she does not realize that you are talking to them. Hi there! - you try again. This time by adding "there" you indicate that you are trying to get the attention of someone in the general area of your voice. The person will understand that you added "there" to show that you are trying to talk to someone "there". Oh Hi Denis! --the person responds. --I wasn't paying attention. I was thinking about something and didn't realize that you were talking to me.--- Other examples. Hi there, I'm over here.........Waving your arm would also help in this case. Is anybody there? Is anybody out there?

As romulus says, it is an informal way to say "Hello to you, there". It is used in a number of situations. If I meet someone I know well on the street, I might say it to them. It would be used if two people know each other and are meeting for any reason. It confirms familiarity. If the person doesn't know you, it is used to establish familiarity, sometimes falsely. If a person I didn't know said it to me, I might be a little suspicious, at least until their motives became clear. Guys in bars often use it to introduce themselves to girls - "Hi, there! You look lonely sitting there." How effective it is depends on how much alcohol the girl has drunk.

"Hi there," in the sense of "I'm over here!" doesn't really work. That would be "Hey, there!" Seems like a nitpick, but 'hi' can really just be used for casual greetings, not to get someone's attention. Also, 'Hi there' is just short for 'Hi, you over there!'

hi Ting, "hi there!" it could be a polite, informal and friendly way of greeting that is mostly between two person in different places. some says, it's just a short term for "hello to you who are there." :)