can I send all the required documents and my passport to the embassy through post?

Hi everyone, please help me answers these questions.
I am a female Vietnamese student in Japan now. I have a conference in China this December.
I received the original invitation letter. But they wrote me as "Mr". Then I have to ask them to fix to "Ms". They sent me the new one through email again. Can I scan it to submit to Chinese Embassy in Japan?
Or I have to ask them to send the new original letter through post for me?
Besides, can I send all the required documents and my passport to the embassy through post? So I donot need to go to Tokyo.
Thank you very much for your concerns.