SQL & PL/SQL

Hi,
I have been assigned a job of sending emails through unix utility(Mailx), based on certain activity in database.
Email needs to be sent on insert/update of a column in one of the database tables.
I am trying to use the block below to call the unix script responsible to send mails:

begin
dbms_scheduler.create_job
(
job_name => 'TPP_SEND_EMAIL_JOB',
job_type => 'EXECUTABLE',
job_action => '/opt/ENV/code/BIL/users/usrbil01/Hemz/sndmailscrpt.ksh',
repeat_interval => 'FREQ=MINUTELY; INTERVAL=30',
enabled => true,
comments => 'Send Email on ISU update'
);
end;
/

sndmailscrpt.ksh: Script to send email is embedded within the shell script

I am getting the below error when i try to run the job using 'exec dbms_scheduler.run_job('TPP_SEND_EMAIL_JOB');'
Error:
ORA-27370: job slave failed to launch a job of type EXECUTABLE
ORA-27300: OS system dependent operation:accessing extjob wrapper failed with status: 2
ORA-27301: OS failure message: No such file or directory
ORA-27302: failure occurred at: sjsec 3
ORA-06512: at "SYS.DBMS_ISCHED", line 150
ORA-06512: at "SYS.DBMS_SCHEDULER", line 441
ORA-06512: at line 1


I am not aware of any db related permissions that needs to be given, is this related to that or is there somethin i need to do for execution to be successfull
Request you to let me know the exact solution and also the steps i need to take in order to ensure successfull execution of this script.

Please also let me know if there is any other way wherein i can call a unix script from a database trigger on run time(i.e, whenever insert/update on a particular column in database)

Regards,
Hemanth