I have a network with 3 sites, two secondary sites and our Head Office site. Each site has its own internet connection which is its default gateway to the internet, but also has a separate high speed wireless WAN link back to Head Office. Our Exchange server is hosted at our Head Office.
From time to time our wireless WAN link goes down. Even though all of our offices still have internet, our secondary sites lose connection to our Exchange server because it is configured to go over our WAN link. Outlook is configured to fail over to RPC over HTTPS but it still resolves our Exchange server to an internal IP which it can not reach.
Is it possible to configure Outlook/Exchange/DNS to fail over to an external IP if the internal IP is not available? Like having 2 MX records for Exchange, one internal and one external?