you should not use any third party server [google... or any else server] to send/receive comment in your application. You should use your own server from which you can send/receive comments with Fire wall protection. Then after you will get all the comments in your Inbox instead of Junk folder.
see below link for the reference.
http://forums.asp.net/p/1404856/3598367.aspx
Please Vote if this helps to you.