We recently deployed servers at a new datacenter for development. Our exchange 2013 server is located at the previous datacenter. Both datacenters have standalone TMG arrays setup for external connections, and for web proxies. There is an IPsec VPN setup between the 2 arrays with a static route.
The problem is servers at the new datacenter are unable to connect with Outlook 2013. The initial setup works with no issues, and repairing the account works as well. But when the users try and start outlook they get an error that it's unable to connect to the server. I can see the requests being allowed in the logging on both TMG arrays both ways, and nothing is being blocked. The IPsec VPN is setup as a route, so NAT is not the issue here. Exchange can be pinged, and OWA works with no issues. Only outlook is unable to connect.