SQL & PL/SQL :: How To Send SMS Through Oracle - Service Not Available Error

I am learning How to send sms thru PLSQL gateway?

I have searched for it on internet & got 1 procedure on OTN. I also tried it. But it is giving me the Errors .

The procedure is as below :

create or replace procedure SEND_SMS(p_sender in varchar2,
p_recipient in varchar2,
p_message in varchar2) as
mailcon utl_smtp.connection;
begin

[code]....

I also tried to Execute the same Procedure. The execute statement is below :

EXECUTE send_sms('myemail@server.com', '9822553277@smsserver.com', 'My Subject', 'My Message');

But i got the errors as :

begin send_sms('myemail@server.com', '9822553277@smsserver.com', 'My Subject', 'My Message'); end;

ORA-29278: SMTP transient error: 421 Service not available
ORA-06512: at "SYS.UTL_SMTP", line 21
ORA-06512: at "SYS.UTL_SMTP", line 97
ORA-06512: at "SYS.UTL_SMTP", line 139
ORA-06512: at "ADMIN.SEND_SMS", line 13
ORA-06512: at line 2