Active directory automatic login to SSRS
This may be a simple matter of Internet Explorer not automatically detecting server2.newdomain.net as an "intranet" site. By default, IE will only do automatic Windows authentication in the intranet zone.

To see if this is the case, you can add "server2.newdomain.net" to the list of trusted intranet sites. Open IE, and do this:


Go to Tools, Internet Options.
Go to the Security tab, click Local intranet, and click the Sites button.
Click Advanced to open the list of sites.
Enter the full name ("server2.newdomain.net") into the appropriate box, and click Add.


If this gets automatic login working, then you'll have to decide how you want to solve the issue. You can specify a list of sites for the trusted intranet zone via Group Policy, but this prevents users from being able to add or remove anything on that particular list. If there's a cleaner way to do it, I'd be interested in knowing too, as we run into this a lot with intranet sites on various DNS domains.