Is it possible to specify a fixed "domain\username" and password for a MSSQL datasource ?
As soon as I choose to specify the user, Tableau server try to identified to the mssql instance using sql authentification.. But my MSSQL instance support only Windows authentification and we will not change this for security reason..
According to this Tableau Server Help section,
SQL Server impersonation could be done
using either Tableau Server Run as User account
or the Workbook / Datasource Publisher's one: