You’ve completed the installation of a new Citrix XenApp 6.5 server and attempt to add it to an existing farm using a remote SQL server as the database server but after entering the credentials and using the Test Connection feature, you receive the following error:
Login failed. The login is from an untrusted domain and cannot be used with Windows authentication.
I found this error message extremely misleading as the first thought I had was that I pointed to a SQL server in a different domain or used an incorrect service account that belonged to a different domain than the SQL server. Both were not the case and the reason that this error message was thrown was because the service account was locked out. The Test Connection feature completed successfully once I unlocked the account: