UNIX for Advanced & Expert Users

Hi,
I am looking for info based on direct experience in using DataStage EE with Unix.
A scenario in the client remote desktop

I work for company Switch, my client is Master.

Notification Activity Stage (IBM Asential Data Stage component)

SMTP Mail server name is blank.
Sender email address is DataSTage@Master.com
Recipients email address is ABC@Master.com
Above works fine, i do get a email, no issue.
But when I say, Recipients email address is XYZ@Switch.com, i do not get any emails.

In the DataSTage Director log it says
Sent message to 'XYZ@Switch.com'
but i do not get any emails.

1. We need to change in "sendmail configuration", where exactly this file should be.
2. The Switch domain needs also needs to be added, can someone please let me know where this is added.

Any idea or suggestion please.
Thank you,

not sure where to exactly add your switch domain. but the location of sendmail is given below

Code:

/etc/mail/
ls
mailcap         sendmail.cf     sendmail.cw     sendmail.pid    service.switch