Login failed error messages in SQL Server – Errors 18456, 18488 and 18470

Error 18470 State 1 –  It occurs when a login is disabled – the error in the log is 18470, not 18456
Error 18456 State 2 – The login does not exist. The login attempt came from a remote machine.
Error 18456 State 5 – The login does not exist. The login attempt came from the local machine.
Error 18456 State 6 – Attempting to use an NT account name with SQL Server Authentication.
Error 18456 State 7 – The login is disabled and the password is incorrect.
Error 18456 State 8 – The password is incorrect. Remember that passwords are case sensitive.
Error 18456 State 9 – The password violated a password policy check.

Error 18456 State 10 – Password checking could not be performed because the domain account being used for the SQL Server service is disabled or locked on the domain controller.
Error 18456 State 11 or 12 – ‘Login-based server access validation failed with an infrastructure error’ or ‘Token-based server access validation failed with an infrastructure error’. Server access failed, the domain controller could not be reached, or a login is denied access due UAC issues. Try running SSMS as administrator or disabling UAC. This error can happen when login with explicit DENY of CONNECT SQL permission attempts to connect to SQL Server.
Error 18456 State 13 – SQL Server service is paused. No new connections can be accepted at this time.
Error 18456 State 16 – The default database for the login was inaccessible, because the database has been removed, renamed, is offline or set to AutoClose.
Error 18488 State 18 – Change password required, when login is added with ‘USER MUST CHANGE THEIR PASSWORD ON FIRST LOGON’ or a login that needs to have its password changed because of the domain or Windows password policy – the error in the log is 18488, not 18456
Error 18456 State 23 – Access to server validation failed while revalidating the login on the connection.  It can happen when users try to login during the shutting down of SQL. It could be the result of connection pooling issues on an overloaded server, or due to some domain issues.
Error 18456 State 27 – The default database for the login was inaccessible, because the database has been removed, renamed, is offline or set to AutoClose.
Error 18456 State 38 – The default database for the login was inaccessible, because the database has been removed, renamed, is offline or set to AutoClose.
Error 18456 State 40 – The default database for the login was inaccessible, because the database has been removed, renamed, is offline or set to AutoClose.

Error 18456 State 46 – Failed to open the database configured in the login object while revalidating the login on the connection. The default database for the login was inaccessible, because the database has been removed, renamed, is offline or set to AutoClose.
Error 18456 State 50 – Current collation did not match the database’s collation during connection reset. Default collation for the login did not match the collation of login’s default database or the database specified in the connection string.
Error 18456 State 51 – Failed to send an environment change notification to a log shipping partner node while revalidating the login.  It can happen if the domain controller could not be reached, or a login is denied access due UAC issues. Instead of built-in local service accounts, try changing the service account for SQL Server to domain or local account.
Error 18456 State 56 – Failed attempted retry of a process token validation.  It can happen if the domain controller could not be reached, or a login is denied access due UAC issues. Instead of built-in local service accounts, try changing the service account for SQL Server to domain or local account.
Error 18456 State 58 – An attempt to login using SQL authentication failed. Server is configured for Windows authentication only.
Error 18456 State 65 – Password did not match that for the user provided.

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