JavaMail API and valid email address

[ssmtech]

Hello All,           I am using JavaMail API to send thousands of emails every day through my application running on J2EE application server... But what i really want to do is, how do i check whether a particular Email Address is Valid or not,if not valid then catch a exception and report it.... Also i meant by Valid email address as to be exsisting on that mail server..e.g "[EMAIL PROTECTED]" .i.e.the user "javamail" should exist on that domain "sun.com"...   Is there any way which i can do the above thing? Also,since i will be sending 1000's of emails every day will it be feasible for me to check each and every email whether it exist or not and then send it.....how much time will it take to do the same...   Please help me out with this,can anybody give me a Detail desciption and Code of how can i do it...   Any suggestions are greatly appreciated   Thanks a million is advance   Sam