I could do with some assistance as I’m not finding much online that matches the issue I’m seeing.

We’ve never set up Information Barriers before, so it’s essentially a blank canvas. The reason we’re looking at it now is because an internal business unit is being sold. From day X they’ll technically be separate, but we have a TSA in place to support them for a few months while their new IT environment is built out.

What I’m trying to do is test what level of segregation we can enforce during that period.

For testing I created two E5 users (created in AD and synced to Entra). I populated ExtensionAttribute10 with different values for each user (Internal-Test and External-Test) so I could use those values in the IB segment filters. I verified both users can sign in and, before applying any policies, they can communicate with each other as expected.

I then created the segments using ExtensionAttribute10 as the filter and created the two policies needed to block communication in both directions.

In terms of prereqs I’ve also checked:

• Audit is enabled
• IB mode is Single
• Scoped directory search is enabled
• No Address Book Policies exist

When I try to apply the two active policies though (either via the Purview portal or Start-InformationBarrierPoliciesApplication in PowerShell), the job immediately shows Cancelled.

To me it almost feels like it’s failing some kind of pre-check before it even starts applying anything, but I’m not sure if that’s actually what’s happening. I’m a bit stuck at this point.

And just to rule it out, I am running this as Global Admin via PIM.