We have implemented Single Sign-on(SSO) with a bit of a difference, Reduced Sign-on(RSO).  The difference is that with SSO, you don't have enter in any credentials when you double click the SFDC icon on your desktop, but with RSO, you are taken to a custom Login webpage where you have to re-enter in your Active Directory credentials.  

So the issue is that when an email alert goes out to the user, the user clicks on the link displayed on the email, but is taken to the native login screen (https://login.salesforce.com) and not our custom login page.  The user is highly confused on what credentials to enter in and gets frustrated with the invalid password attempts.  

We cannot redirect everyone on the network going to the https://login.salesforce.com URL to go to our custom login page as the Administrator of SFDC are not RSO enabled.

What could I do for the users that are RSO enabled and click on the email link and expect to find the correct login page?

Regards,

Shaveen.

South Africa.