internet related AT commands in SIM5216E

[pandi_2u]

recently I bought a 3G shield from elecfreaks. In that I tested AT commands for calling related and camera and SD card related operations. But while trying to send email I got network error. can anyone please help me to solve this problem. below are the commands I used to send email and the replies from sim5216E modem.

at+cgsockcont=1,"IP","airtelgprs.com"
reply -> OK

at+csockauth =1,0
reply -> OK

at+smtpsrv="smtp.mail.yahoo.com",465
reply -> OK

at+smtpauth=1,"my_mail_id@yahoo.com","my_password"
reply -> OK

at+smtpfrom="my_mail_id@yahoo.com","my_name"
reply -> OK

at+smtprcpt="to_mail_id@yahoo.com","to_name"
reply -> OK

at+smtpsub="test mail"
reply -> OK

at+smtpbody="Welcome"
reply -> OK

at+smtpsend
reply -> +SMTP: OK

+SMTP: NETWORK ERROR

I recharged my sim card with 3G internet pack.
And I tested the 3G frequency of modem (UMTS 2100 MHz) with the frequency we are using for 3G network in INDIA. Both are same.

Please help me to solve this.