Hi All,
any help can help on following issue.

SQL> exec send_mail_to_admin('This is the title','This is the subject');
BEGIN send_mail_to_admin('This is the title','This is the subject'); END;

*
ERROR at line 1:
ORA-20001: 421 Service not available
ORA-06512: at "SYS.UTL_SMTP", line 83
ORA-06512: at "SYS.UTL_SMTP", line 121
ORA-06512: at "SCOTT.MAIL_PKG", line 48
ORA-06512: at "SCOTT.SEND_MAIL_TO_ADMIN", line 4
ORA-06512: at line 1

Thanks