As a company with two separate trading arms that is looking at sharing resources more closely, but still retain our own IT infrastructure. I was thinking of suggesting a single Forest solutionwhich contains two separate name spaces i.e. Company1.net and Company2.net. The reason for this idea is that using Exchange 2007 the requirement is to have Shared address books, Calendar free busy information as well as the means for anyone from Company2 or 1 to be able to email out as the other company. Or, are the Exchange requirements available between a Forest to Forest trust, especially the Calendar Free Busy? Thanks,

Hi,Yes, it requires corss forest trust if you are planning to configure per-user free/busy for detailed information, otherwise organization wide free/busy configuration gives you default level of free/busy which doesn't require trust.Check this article for further details and steps to configure it between two Exchange 2007 organization...How to Configure the Availability Service for Cross-Forest Topologieshttp://technet.microsoft.com/en-us/library/bb125182.aspxAmit Tank | MVP - Exchange | MCITP:EMA MCSA:M | http://ExchangeShare.WordPress.com

Thanks for the info. If we did go for two separate forest would we then have to create an email contact on the opposite Exchange environment so that we could send / receive as their email address? As I thought the email MX record could only be associated with one system?Thanks

Hi Rick,Yes, MX record could be associated with one system. These email contacts are to obtain free/busy information and for internal mail flow between these two organizations only.Amit Tank | MVP - Exchange | MCITP:EMA MCSA:M | http://ExchangeShare.WordPress.com