I am getting a failed login message in the SQL Server error logs however, nothing actually failed? I have a server which runs third party software (called Visualcut) to email Crystal Reports to our users.

When I log onto the Visualcut Server, I can open the software and then preview a report. This will ask me to enter a username and password (for an Microsoft SQL account) and then the report will display with no errors however, whenever I do this, an error is logged in the SQL Server error logs as follows:


  10/26/2015 08:15:39 Logon Unknown Login failed for user ''. Reason: An
  attempt to login using SQL authentication failed. Server is configured
  for Windows authentication only. [CLIENT: 10.10.10.26]
  
  10/26/2015 08:15:39 Logon Unknown Error: 18456 Severity: 14
  State: 58.


I don't understand why the report would authenticate seemingly without any issues however, the log file states otherwise.

I would like to add that our SQL Server is configured to use mixed authentication.
From Aaron Bertrand's blog on Troubleshooting Error 18456


  Error: 18456, Severity: 14, State: 58.
  Login failed for user ''. 
  Reason: An attempt to login using SQL authentication failed. Server is configured for Windows authentication only.


State 58 occurs when SQL Server is set to use Windows Authentication only, and a client attempts to log in using SQL Authentication.

You have to Change Server Authentication Mode and restart sql server, if you/your software requires SQL Server authentication and your sql server is configured for Windows Authentication.