Description: In crmmail mail box on exchange server thousands mails in undeliverable folder and tens mail in inbox. In application event log on exchange server multiple error messages from MSCRMExRouterService the error begins like this:
Microsoft.Crm.Tools.ExchangeConnectorService.ExchangeSinkServiceException: Verifying before delivery message: CRM - Account Hierarchies in mailbox: CRMmail failed (System.Net.WebException: The request failed with HTTP status 401: Unauthorized.
Fix: change logon account for CRM router service from system local to account for CRMMAIL mail box, enter CRMMAIL account as member of PrivUserGroup.
According to Microsoft CRMMAIL mail box should be empty at all time. The messages should be evaluated and deleted immediately upon receiving.