Hi! We have one AD site that hosts our Exchange 2007 servers, 2 cas/hub and several E2007 mbx servers. Can we add a Exchange 2010 cas and an E2010 mbx server to this site to run a pilot for some users. I understand that the external owa address needs to be different than the one in E2007. Would this be possible?What happens with autodiscover, I read something about outlook 2007 and above will receive them in order of installation from the SCP (oldest first). Regards, UC

You'll need to prep the forest first: http://technet.microsoft.com/en-us/library/bb125224.aspx Be sure to put a trusted certificate on the 2010 CAS as soon as possible, otherwise, your clients may get trust errors. Do not use the self-signed cert . There is no guarantee that the 2010 CAS wont be used for autodiscover, so use a trusted cert - I'm repeating myself :) If the 2010 CAS is internet-facing, use a trusted 3rd party cert. Also take a look at the Deployment Assistant: http://technet.microsoft.com/en-us/exdeploy2010/default.aspx

Thanks for a fast reply! I noted the certificate in Bold letters in my planning document for this project :) But as long as I get the certificates it won't break anything for my E2007 users? And if the pilot and poc is accepted we should be able to move the external url to E2010 boxes and add the legacy redirect and then start to move our users to the new servers?

Thanks for a fast reply! I noted the certificate in Bold letters in my planning document for this project :) But as long as I get the certificates it won't break anything for my E2007 users? And if the pilot and poc is accepted we should be able to move the external url to E2010 boxes and add the legacy redirect and then start to move our users to the new servers? Correct. If you use trusted certs, your Outlook clients will be ok no matter what server they are on. And yes, on the second question as well.