i would like to confgure my sendmail as the smart host for my open xchange intranet server, any one idea how to configure it?

Thanks.

I'm no SMTP wizard, but to forward SMTP all you should have to do is make sure that the Open Xchange server can initiate connections to port 25 (SMTP) to the machine running sendmail, and make sure that sendmail is configured to relay all mail from these hosts (although it might be a good idea to limit relaying to the domain(s) you know the Open Xchange host sends mail for).

Let me understand this, is this what you are trying to acheive?

OpenExchange -> Sendmail box -> Internet

Or this?

Sendmail box -> OpenExchange -> Internet ?

If it is the former then you just have to set the sendmail box up as a normal box, but only allow the ip address of the OE server to relay, if the second then in sendmail.mc you will find an option called "define(`SMART_HOST',`mail.my-site.com')" whereby mail.my-site.com is where you need to put the name of the OE server. Now stop sendmail, do make -C /etc/mail and re-start sendmail and you should see the email going from the sendmail box to the OE server and out to the wide world.

If it is for incoming then that is for a whole different kettle of piscines....