Priority value out of range: Exchange Online Transport Rule Deployment

Deployment Context

The goal is to create a set of transport rules in Exchange Online via PowerShell with explicit priority values so that rule evaluation follows a deterministic order. Constraints include the undocumented behavior that identical priorities are resolved by creation timestamp, and that Import‑TransportRule defaults priorities to 0.

Observed Uncertainty

During recent deployments, the engine emits “Priority value out of range” when a priority exceeds an undocumented threshold, yet the rule still appears in Get‑TransportRule without error. Disabling and re‑enabling a rule resets its priority to the default, breaking existing chains.

Questions

1. What criteria does Exchange Online use to order rules when multiple rules share the same priority?
2. What is the exact upper bound for the Priority parameter before the engine issues the warning?
3. How can we preserve a rule’s priority after it is disabled and re‑enabled?