How to secure an Exchange mail server?

Question

Burglary protection

Good day to all!
The event log constantly flashes the Credential Validation (Audit Failure) event
with ID 4776 (non-existent user)

The computer attempted to validate the credentials for an account.

Authentication Package:	MICROSOFT_AUTHENTICATION_PACKAGE_V1_0
Logon Account:	justin
Source Workstation:	mailserver - имя почтового сервера на Exchange 2010
Error Code:	0xc0000064

And they are different - justin, newsletter, spam, customers and so on.
How to conduct a security audit and get rid of unwanted users from the outside?

Answer 1

Relax and enjoy.
If you are not afraid, you can try setting up wail2ban