Good Deal, I'm glad you solved it!
I'm sorry, I cannot explain why you had the trouble. I am just a customer here like you - the support people will likely be able to give you a better idea of what might have happened, if you send a support request and ask them.
Yes, DreamHost supports both POP3 and IMAP email directly, and you can access POP3 with any client, and IMAP with any IMAP client and webmail (set up at "webmail.yourdomain.cn").
I'm not sure what precisely you are looking for in regarding "how about the international language capability?", but I know that utf-8 is supported throughout, and there are many sites hosted on DreamHost in Chinese.
People's experience with Gmail and Google Apps varies, as does their experience with DreamHost email - most are happy with wither, though some feel that Gmail is more reliable and/or has better spam filtering.
My experience has been that DH reliability is fine (as good as Gmail for me), but I agree that Gmail does a better job of filtering spam - either is fine for me as I use POP3 and let Thunderbirds filtering handle my spam (and it dows a fine job for me, once thoroughly trained).