Ensure sign-in to shared mailboxes is blocked

Why This Matters

Shared mailboxes are designed for collaborative email access, not for interactive user sign-in. If sign-in is not blocked, an attacker who compromises credentials for a shared mailbox can access it directly, bypassing delegated permissions and auditing. Blocking sign-in reduces the attack surface by ensuring shared mailboxes cannot be used as rogue accounts.

What Aether365 Checks

This check verifies that the accountEnabled property is set to False for all shared mailboxes in your tenant. It appears in the Aether365 dashboard under the Microsoft 365 security checks section.