Hi,

I would like to find out for Exchange On Premises with EOP setup for belows:

1)  If Exchange 2010 existing domain has autodiscover CNAME to autodiscover.outlook.com.
     What is the best way to go about for new Exchange 2013?

2) Although CNAME for autodiscover no needed as told in Exchange on Premise setup, is there any advantage to maintain such?

3) Do the CNAME autodiscover will switch to new Exchange 2013 in the co-exist environment Exchange 2010 and Exchange 2013?

4) Should we remove the CNAME instead? 

• Moved by Jason Johnston [MSFT]Microsoft employee Thursday, June 04, 2015 2:25 PM Not a development question.

Hi,

If all mailboxes are hosted in on-premises Exchange server and you just want to use EOP to protect them which is known as a tandalone scenario, there is no need to create CNAME record for autodiscover service. For more information about this scenario for ECP configuration, please refer to:

https://technet.microsoft.com/en-us/library/jj723153%28v=exchg.150%29.aspx?f=255&MSPPError=-2147217396

In the co-exist environment Exchange 2010 and Exchange 2013, we can just point your domain name with autodiscover service (autodiscover.domain.com) to Exchange 2013. Also change the primary host name (mail.domain.com) to Exchange 2013 and publish the Exchange 2013 to the Internet. Then configure the external URLs for Exchange 2013 to use mail.domain.com and clear the Exchange 2010 external URLs to $null.

In this way, the external service request would connect to Exchange 2013 from Internet and proxy the request to Exchange 2010 internally for all Exchange 2010 mailboxes.

Regards,