@AllinTrendy: "Do I have to reply back to all messages that I received even its an automated message from a people who advertise their services?" As it says right on your Star Seller page and elsewhere, you need to reply to the FIRST message of EVERY NEW INCOMING THREAD within 24 hours. It does not matter who sent it, the subject matter, if it is a duplicate or blank or anything else. If it is SPAM then it should be marked as such. Remember that the Star Seller metric is NOT all new messages but only the first message of all new incoming threads.
Unless something has changed recently, you can only mark a message as SPAM using the buyer app or a browser, the option is not available in the seller app.
Although it probably will not help for the December star, if the unanswered new thread is not a Help Request, at least for the time being, it appears that marking an unanswered new thread as SPAM (even after the 24 hour deadline has passed) will cause your reply percentage to change in a day or two if the original message was within the current star seller period (but not retroactively). Note that subsequent messages from that account may go directly to the SPAM folder.
You might want to reread the Star Seller rules so that you are not surprised by something else.
