We are in the process of migrating Exchange 2007 to 2013 in coexistence mode. Since we have never done this before I have some questions in regards of how this is accomplished. Right now the current 2007 values point to i.e owa.domainold.com. We are planing to move everything to webmail.domainnew.com. (let me be clear Internally the Active directory domain will not change and will remain the same).
With coexistence we need to purchase SSL certs for webmail.domainnew.com, autodiscover.domainnew.com and for the legacy am I purchasing legacy.domainew.com or legacy.domainold.com. Also how are we transitioning users (Outlook clients) because if we start using legacy.domainold.com or legacy.domainnew.com they will loose connectivity to the Exchange servers.
I don't know if this is clear enough but would like some guidance.