business e-mails

[diehard]

hello

I am applying for an internship in the USA at the moment. I received some answers by e-mail. They start their e-mails with "hello mark" and at the end they write their complete name. My question: Do I answer them with "Hello" and their first name or with "Hello Mr." and their last name.

I know it is an funny question but I don't have any clues about it.

Thank you

Mark

[MLS]

I personally would start with "Dear Mr. xyz"

It ist better to use this formulation as you are not familiar with those people.

[diehard]

thank you for your answer.

On the other hand, however, they are using my first name and they don't know me too. And I don't think that I am a lot younger than they are.

Do you think that it is really bad to use their firstname?