[Solved] How do I configure Unix Mail Server to use another Mail Exchange Server

We have configured our mail unix server and can send out emails automatically from applications running on unix to different people in our company as well as outside our company. However there is an outside client who is not receiving these emails because the settings on their mail server cannot recognize our unix mail server and yet if we send emails from another mail exchange server they get them. I guess we need to set and configure our mail unix server to use our main mail exchange server which is recognised by their mail server. Please can anyone help! Where can I find documentation to configure our mail unix server to use our main mail exchange server. Thanks.

on HP-UX 11.11 (thats all I have...)

A)
look in /etc/mail, save the file sendmail.cf:

cp -p sendmail.cf sendmail.cf.ori

edit with vi sendmail.cf and look for this stanza:

# "Smart" relay host (may be null)
DS

and modify accordingly

#DS
DSsmtp.mydomain.com

So you append to DS the fullname of your exchange mail server.

B)
1) stop star the sendmail in /sbin/init.d
2) set environnment variables:
export charset=iso8859-1
export encoding=8bits
to put in file=>.mailrc? ( I put a .mailrc in home directories of the people having right to use the mail)

Another possibility is that you do not have reverse DNS set up so that the public ip address that the email originates from does not resolve to the domain name of the email address.

Thanks. We shall try it

Thanks, the first solution worked