This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
From what I can understand of that code, you are trying to use the SMTP server at smtp.comcast.net to send e-mail. And that server says you have to authenticate yourself to it. So, do that. Your code doesn't do any authentication that I can see.