Symptoms

We are going to change our email from Exchange Server 2013 to Exchange Online and have to test on our Dev Environment first. When we rerun the K2 blackpearl Setup Manager, we encounter the problem with Exchange Server Configuration, we set the "Configure Exchange Online", input the Email address and Password and EWS URL, the mailbox can be accessed through O365 email web.
 

Diagnoses

The client also tried testing the EWS URL through "https://outlook.office365.com/EWS/Exchange.asmx", it showed the error "The EWS URL could not be validated"
 

Resolution

The issue was resolved through using the below workaround:

1. Proceed with installation when K2 Setup Manager prompted that the EWS URL cannot be validated.

2. Once done, go to eProgram Files]K2 blackpearlHost ServerBin, and open ConnectionStringEditor.exe

3. Select your Exchange connection string, and change Autodiscover to False

4. Create a simple workflow and test.