Hello Deepak,
Did you specify the recipient address correctly and the address type 'U' (Internet address) ? Pls chk this.
Also before testing your program, it is better to test from SBWP T code. Here click on new message, give your id under recipient and send and test the mail from here.
Are using the correct Mail Host (IP address) and Mail Port (usually 25) in SCOT under node SMTP ? Pls chk.
Also please check these discussion threads once which were already resolved on the same issue.
http://scn.sap.com/thread/3330692
Also pls check this note once. SAP NOTE - 455140 Configuration of e-mail, fax, paging or SMS using SMTP, specially NODES section:
I hope it helps!
Thanks & Regards,
Lakshmi S