While setting up the CRM 2015 using multi-server topology as outlined here, one of the issues I encountered is that the Office 2013 installed on Windows 7 Client could not connect to Exchange Server 2013. The error message from Outlook reads along the lines shown in the snap shot below.

This occurs if a default gateway is not configured on Outlook 2013 Client computer. The following is the work around:

Use Reg.exe tool to disable the DefConnectOpts value.

Querying the result of above addition

The Microsoft support link here provide more information on this issue. The information detailed here references Outlook 2007, the same is applicable to Outlook 2013 with the exception that the path to the registry will be …\Microsoft\Office\15.0\Outlook\RPC…