I have noticed a thousands of audit logs failure with Event ID:4768 with error "0x6" and username Host coming from our exchange servers to domain controllers:
A Kerberos authentication ticket (TGT) was requested.
Account Name: host
Supplied Realm Name: our domain
User ID: NULL SID
Service Name: krbtgt/our domain
Service ID: NULL SID
Client Address: ::ffff:( the IP of the exchange)
Client Port: 40486
Ticket Options: 0x40810010
Result Code: 0x6
Ticket Encryption Type: 0xFFFFFFFF
Pre-Authentication Type: -
Certificate Issuer Name:
Certificate Serial Number:
Certificate information is only provided if a certificate was used for pre-authentication.
Pre-authentication types, ticket options, encryption types and result codes are defined in RFC 4120.
Note that we have exchange 2019 CU12
What cause this failure ?