Mail servers

[Sreenivas]

Hi,     I have already posted this question once, sorry for posting this again. As i am strucked up at this piont in our network design it would be great if any body could give me quick suggestion.       I have a requirement like i have to setup two mail servers, One of these two will be in public domain with public ip address which could collect mails from other domains. And the other mail server should serve for internal mails which will be in our private network. supposing mail server external is     xxx.com with ipaddress 196.x.x.x internal mail-server is   aaa.xxx.com with ipaddress 10.x.x.x if i say mail to [EMAIL PROTECTED] from pop client it will go to aaa.xxx.com and delivers it to [EMAIL PROTECTED] if i say mail to [EMAIL PROTECTED] from pop cleint of aaa.xxx.com it should get delivered to [EMAIL PROTECTED] [EMAIL PROTECTED] will get mail saying that mail from [EMAIL PROTECTED] etc. when he says reply it doesnot go to [EMAIL PROTECTED] because aaa.xxx.com has non routable ip-address i.e 10.x.x.x. to overcome this i want to do like this.  if it is internal mail like [EMAIL PROTECTED] it should go to mail server aaa.xxx.com and deliver the mail. and if it is external mail like [EMAIL PROTECTED] it should go to our external mail server xxx.com and go out with the from address as [EMAIL PROTECTED] even if it is sent from [EMAIL PROTECTED] the external mail server should take take care of stripping off aaa from [EMAIL PROTECTED]  What is the simple way bto achieve this. Please any on help me.   This kind of setup is only to lessen the traffic due to local mails like from [EMAIL PROTECTED] to [EMAIL PROTECTED]  on the point to point link that we have in between our external and private network.   I would like to have internal and external mail servers configured on RH Linux with Sendmail. As i have to submit report on this to my boss in couple of days, Please throw your suggestions imdtly.   Thanks for any help in advance.   Cheers Sreenivas M