Problem with sending mail from Oracle 9.2

Hello

I have problem with sending mail from some mailhosts. The procedure is working fine on most hosts, but here is example when it's not working. The output is: PL/SQL procedure successfully completed, but mail is not sent.

This is the procedure:

declare

  msg_to varchar2(100) := 'ante.despalaatovic@pos-st.hr';

  msg_subject varchar2(100) := 'subject';

  msg_text varchar2(100) := 'text';

  c utl_smtp.connection;

  rc integer;

  msg_from varchar2(50) := 'ante.despalatovic@vip.hr';

  mailhost VARCHAR2(30) := 'mail.vip.hr';

BEGIN

  c := utl_smtp.open_connection(mailhost, 25); -- SMTP on port 25

  utl_smtp.helo(c, mailhost);

  utl_smtp.mail(c, msg_from);

  utl_smtp.rcpt(c, msg_to);