This article was created in response to a support issue logged with K2. The content may include typographical errors and may be revised at any time without notice This article is not considered official documentation for K2 software and is provided "as is" with no warranties.


Client event notifications are not sent out and an error message appears.


The following error is logged when the issue occurs:

"Error","MessageBus","61012","ConnectionError","ExchangeWebServicesOrigin","61012 Exception from message source System.Net.WebException: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel. ---> System.Security.Authentication.AuthenticationException: The remote certificate is invalid according to the validation procedure.

Troubleshooting Steps

These steps are applicable to K2 environments integrated with Exchange On-Premise.
  1. Open the Connection String Editor in [\K2 blackpearl\Host Server\Bin]:

  2. Choose any of the EWS Exchange connection strings on the left panel: 

  3. On the right panel, copy the value of the URL Connection String Property:

  4. Open this URL on the browser and ensure that there are no certificate errors or warnings:

  5. If any errors appear, please raise this with your Exchange Server admin.