Can I mail my Gambian passport to The Chinese Embassy for visa application?

I live in the US as a permanent resident here, but my residency card is expired. I have the official letter of extension, that says it serves as the extension for employment and travel. I was denied and they said the only way to obtain mine is to bring my Gambian passport to The Embassy in Senegal, which is not possible. Can I mail my passport and application in? Thank you.