Mail Flow & TransportTransport Rules & Mail Flow Rules

Transport Rules & Mail Flow Rules

30 mins

Understanding the Concept

Transport rules (also called mail flow rules) are policies applied to messages as they pass through the transport pipeline. They consist of conditions, exceptions, and actions that can modify, redirect, or block messages.

Rules can add disclaimers, encrypt messages, forward copies to compliance officers, block attachments, or route messages to specific connectors. They are evaluated in priority order, and processing can stop after a match.

Common use cases include adding legal disclaimers to external emails, enforcing TLS for specific partners, blocking messages with sensitive content, and routing messages through compliance review.

Key Points

•Rules have conditions, exceptions, and actions

•Priority determines evaluation order (lower number = higher priority)

•Stop processing option prevents subsequent rules from running

•Rules can target specific senders, recipients, or message properties

•DLP policies integrate with transport rules for data protection

•PowerShell: New-TransportRule, Set-TransportRule, Get-TransportRule

Why This Matters

Transport rules are one of the most powerful tools for controlling message flow and enforcing organizational policies. They enable compliance requirements, security measures, and business logic without third-party tools.

Common Mistakes to Avoid

✗Creating conflicting rules without proper priority ordering

✗Using Stop Processing Rules inappropriately, skipping important rules

✗Not testing rules in test mode before enabling in production

Interview Discussion Points

💡Describe a complex transport rule you implemented and its business purpose

💡Explain how rule priority affects message processing

💡Discuss how to implement email disclaimer requirements using transport rules

MS-203 Exam Tips

📝Know how to create rules for common scenarios: disclaimers, encryption, forwarding

📝Understand rule priority, exceptions, and the Stop Processing Rules action

📝Be familiar with both EAC and PowerShell methods for managing transport rules

Understanding Mail Flow in Exchange Online

Connectors & Partner Mail Flow