Appropriate way to address a business associate by email

[danieru_s]

The company that I work for has offices in Japanese. I've never corresponded with anyone who works there, so I'm not sure what appropriate behavior is.

If someone emails me and signs the email using her first name, is it acceptable for me to reply back Hi FirstName or should I reply Hi LastName-san? I assume that the way she signs her email is an indication of how she wishes to be addressed or is she just using her first name because she expects that Americans (or in my case Canadians) wouldn't understand?

[jkid]

I assume that the way she signs her email is an indication of how she wishes to be addressed or is she just using her first name because she expects that Americans (or in my case Canadians) wouldn't understand?

Probably a bit of both. I would address them as they've signed their email.