Hi My company use Exchange2003 as primary mail server communicate worldwide. I would like to know how to setup a internal mail server only communicate internal staffs, i dont want to create another email address for users internally, I would like to keep using their primary email address (xxx@xxx.com) as for my Internal email server. This is just for use within company.

Most companies utilize the same exchange server for both internal and external and have a front end server in the DMZ for security. How are you expecting users to get the mail? You can setup an acct on the unix box and they can check it using mail or pine or one of the other programs. Although, you would be seriously impacting the user experience.

i think you can use exchange for internal and external email. you dont need another MTA for doing this. The same applies with sendmail as an MTA. I would find it hard for you to have a different MTA for internal email and another for external. The MTA can be utilised for both. This is a common setup. hope it helped