I have a Web site application. It is defined to use a connection string to SQL Server with Integrated Security=True. The IIS of that virtual directory is set to an application pool. That application pool is used for other Web site. It works. The application is set to use a specific username.

However, on the new Web site, when I try to do a SQL Server command, I get:

Login failed for user 'NT AUTHORITY\IUSR'.

I cannot understand why that Web site is trying to use that account when the application pool is set for a specific user.

Anyone would have an idea what could be a factor here?