Thanks for the article Ross, it is very informative. I do have a question on legacy URL regarding Outlook connectivity to non-Internet facing Exchange 2007 site.
You stated this in the article: "The legacy namespace provides connectivity for OWA, is the namespace returned in Autodiscover responses (e.g., Exchange Web Services URL), and provides access to Exchange 2007 mailboxes that exist in non-Internet facing Active Directory sites."
I actually thought that legacy namespace is only needed for OWA and EWS and not for Outlook Anywhere Exchange 2007 clients because these connections are proxied from EX2013 CAS to EX2007 CAS. In fact, we are in the middle of a migration right now and I can confirm that it does work this way because Outlook Anywhere clients that have mailboxes on EX2007 in non-Internet facing site can successfully access their mailboxes through EX2013 CAS and we do not have legacy namespace configured. However, EWS is not working and some functionality in Outlook clients is not available (Out-of-office for example, but Availability is working nicely).
Sorry If I misinterpreted your wording.
Regards,
Dinko