We are planning to migrate Exchange 2010 to Exchange 2013.
I understand that we need to upgrade the CAS to 2013 for Internet Facing.
What about mail flow. Currently, Internet mail flows to Exchange 2010 (single site). Can I keep it for sometime after introducing 2013 and do the cutover of HUB once all the mailboxes are moved to 2013? Or I have to get the mail flow to 2013 first.
Also, how does HUB 2010 transfer mail or receive mail from 2013? Does it get from the CAS proxy in 2013 or from HUB?
Thanks!!!