Microsoft US Sovereign Cloud Myth Busters - A Global Address List (GAL) Can Span Multiple Tenants

Great explanation!  Definitely a worthwhile read!

In the effort to reduce / eliminate Spill.  There is a line of thought around providing a naming convention within the universal GAL to identity the correct person within the organization in regards to  ITAR/DFARS/etc....   i.e. Mary Smith (Gov) vs. Mary Smith, the counterpoint is that the organization does not want to call attention to their government workers / cleared personnel. 

Obfuscated identifiers could also be invoked;

• Mary Smith (A) - Commercial Employee
• Mary Smith (B) - US Citizen
• Mary Smith (C) - OCONUS 

Next option could potentially be:

"Tool Tips" within the Outlook client triggered on GAL attributes

• Tool Tip Display - This "Mary Smith" is outside the the Government Enclave are you certain this is your intent.
• Tool Tip Display - Preventing sending to "Mary Smith" OCONUS
  • Create escalated exception process

Next option could potentially be:

Evoking "AIP Encryption" on the GCC High side environment for all personnel who are placing commercial aliases within email.  This can be accomplished by creating groups.  https://docs.microsoft.com/en-us/azure/information-protection/prepare

And not but least a combination of some or all of the previously mentioned options above.  Open to thoughts and comments -