My client has got many sub-offices, and one head office. The headoffice has a domain name: business.com

All users in the many sub-offices need to have a headoffice email address: [email protected] Anyone not in the head office will need the email forwarded to an external email address. All users in the head office will have their email delivered to Microsoft Exchange. Users are listed in Active Directory under two different OU's: HeadOffice or SubOffice.

Is this something able to be configured? I've done some googling, but I can't find any examples or businesses set up this way.

Edit: Postfix will accept all email, will need to determine to forward the email to an external account or alternatively have it delivered to MS Exchange.

I've done some reading about MS Exchange and that you can 'mail-enable' contacts for forwarding - but I don't know if each AD account requires an Exchange CAL?

The end goal is to forward email to external accounts to sub offices or accept email for head office.

Maybe I don't need to worry about Postfix to perform this task.....

http://www.windowsitpro.com/article/exchange-server-2010/exchange-server-licensing-some-of-your-questions-answered

"What about client access licenses (CALs)? You need one CAL per user who will connect to Exchange. Although it might not be 100 percent precise, I prefer to think of it as one CAL per mailbox; there are exceptions for users outside your organization, automated tools that use mailboxes, and so on. Exchange doesn't enforce this limit, so it's on you to ensure that you have the correct number of CALs for the set of clients you support."