Assume that the Client Throttling policy is configured, and that DiscoveryMaxMailboxes is set to Unlimited in Microsoft Exchange Server 2013. In this situation, when a user who falls under Client Throttling policy tries to run the New-MailboxSearch cmdlet, the following error message is received:
WARNING: An unexpected error has occurred and a Watson dump is being generated: No value.
VERBOSE: [17:51:41.571 GMT] New-MailboxSearch : Admin Audit Log: Entered Handler:OnComplete.
This is a known issue in Exchange Server 2013.
To work around this issue, configure DiscoveryMaxMailboxes to have a numeric value in the throttling policy.