Mail server problem

Hi all,

 We have an ubuntu 10.04 server and windows 2003 server. I want to configure mail server on ubuntu and then i want to send mails to users which is in Active Directory in windows 2003 server. 

I have little bit knowledge on above scenario. By adding linux to windows domain. But am confusing how to start. Can anybody explain about this problem.

Thanks,

Thanks for your reply,

 Which lines we have to add in samba server. And then tell me some steps to add domain.

Thankyou.