oracle utlmail problem

[veledrom]

This what i do; Can anyone tell me whay i receice an error.

1- Run "SQL Command Line".
2- connect / as sysdba . "No error".
3- @?/rdbms/admin/utlmail.sql . "Created and no error".
4- @?/rdbms/admin/prvtmail.plb . "Created and no error".
5- GRANT execute ON utl_mail TO SYSTEM; "No error"
6- Open my "Oracle SQL Developer" GUI.
7- Type code blow as it is and run;

BEGIN
  EXECUTE IMMEDIATE 'ALTER SESSION SET smtp_out_server = authsmtp.streamline.net';
  UTL_MAIL.send(sender => '[e-mail]',
            recipients => '[e-mail]',
               subject => 'Test Mail',
               message => 'Hello World',
             mime_type => 'text; charset=us-ascii');
END;

8- I receive this error;

Error starting at line 1 in command:
BEGIN
  EXECUTE IMMEDIATE 'ALTER SESSION SET smtp_out_server = authsmtp.streamline.net';
  UTL_MAIL.send(sender => '[e-mail]',
            recipients => '[e-mail]',
               subject => 'Test Mail',
               message => 'Hello World',
             mime_type => 'text; charset=us-ascii');
END;
Error report:
ORA-00922: missing or invalid option
ORA-06512: at line 2
00922. 00000 -  "missing or invalid option"
*Cause:    
*Action:

I use:
- Oracle 10g Express edition
- Win XP Prof SP2

Thanks