@digiconz the only way around it that I've seen is to use different email addresses as well. Setup the real email address in production and a fake one in sandbox, and you can have two different passwords.

Then you will have two sets of credentials in ADFS for a single user. Theoretically one set of credentials should work for both production and sandbox because both are now under same framework or domain. I haven't tried SSO via ADFS for sandbox yet, will play around after suiteworld.