Problem

Microsoft Teams and Outlook 365 stop working after some time when Desktop Validator is enabled.

Explanation

It is a known issue that Outlook 365 / Teams will eventually fail when Desktop Validator is configured with a check in the box “Remove other CAPI revocation providers”. These Microsoft products appear to require the Microsoft validation provider cryptnet.dll to be included in the system registry.

However, it appears that as long as cryptnet.dll is the second choice in the registry (behind Desktop Validator’s tmwdcapiclient.dll), Outlook 365 / Teams will work – and will actually use Desktop Validator for certificate validation.

Workaround

We recommend that customers who use Outlook 365 / Teams do NOT enable “Remove other CAPI revocation providers”. So far, Microsoft has not been willing to correct this problem with their software.