SQL Server connection failed for domain user from Mac OS machine

I have SQL Server 2008 R2 SP1. I am using connection string to connect to SQL Server. In connection string I am passing the driver path, server name, TCP port number, user name with which I want to connect, password, DSN name, TDS driver version number, db name. - I am using Free TDS driver for connecting from Mac OS machine. - On SQL server side I am having Windows authentication mode. - When I tried to connect by entering the user name and password of the user who has installed the SQL server or admin of the SQL server, it works fine. But if I try with normal domain user, I am getting the SQL Server connection failed error. After searching about it I found that some authentication is failing. Can anyone help me in resolving this issue? I believe that some settings need to be changed or there should be some modification on connection string.