> Microsoft Windows Server has detected that NTLM authentication is presently being used between clients and this server. This event occurs once per boot of the server on the first time a client uses NTLM with this server.
NTLM is a weaker authentication mechanism. Please check:
Which applications are using NTLM authentication?
Are there configuration issues preventing the use of stronger authentication such as Kerberos authentication?
If NTLM must be supported, is Extended Protection configured?