Transport rule header internal email

Brass Contributor

I have two organizations . one is gcc-high and the other is a commercial tenant. The distribution groups in both organizations are restricted so they won't accept email from an external sender. Can i create a transport rule that will modify the header when received from a particular domain and set the header so the receiving exchange organization considers the email  "internal" ? If so can you please explain how to configure the rule ?

2 Replies

@skipster311-175 I understand that you need to allow emails sent to a distribution list from specific external domains only.


In order to achieve this, you need to do it the other way around. Modify first your distribution list to allow emails from external senders.



Then create a a transport rule that would block emails sent to the distribution list with the exception from specific domains. This should be the conditions:

  • Apply this rule if -> select "The message..." -> "To or Cc box contains this person"
  • Select the distribution list
  • Add another condition
  • select "The sender..." -> "is external/internal"
  • Select "Outside the organization"
  • Do the following -> "Block the message..." -> "Delete the message without notifying anyone"
  • Except if -> "The sender is..." -> "Domain is..."
  • Add the domain that you wish to be received by the users


You transport rule would look like this:




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but we have thousands of distribution groups, so unless this could be scripted its not realistic solution