Exchange 2010 : Create a Message Send Size Limit For A Subset Of Users Within an Exchange Organisation

Exchange 2010 : Create a Message Send Size Limit For A Subset Of Users Within an Exchange Organisation

We recently encountered a requirement to limit a subset of users to a maximum send size without imposing this organisation wide – this was achieved this using a transport rule, the steps are outlined below.

  1. Create a Distribution Group that contains all your Exchange Users that you wish to limit email size for. For this example this group has an email address of [email protected]
  2. Create a new Dsn Error message: New-SystemMessage -DsnCode 5.7.50 -Language En -Internal $True -Text ‘Your message has not been sent as it exceeds the maximum allowed message size of 20MB. Please contact the helpdesk for support on 123 or click here to raise a support ticket <a href=”http://helpdesk/riaseticket.html”>Open Support Ticket</a>.’
  3. Next create a new transport rule (change the [email protected] email address to reflect the group created in step 1) : New-TransportRule “Block Internal Email over 50MB” -FromMemberOf “[email protected]” -attachmentSizeOver 50MB -RejectMessageEnhancedStatusCode “5.7.50” -RejectMessageReasonText “Your message has not been sent as it exceeds the maximum allowed message size.” -SentToScope “InOrganisation”
  4. Verify the priority of any other transport rules configured in your Exchange Organisation.
You can now test this by attempting to send an email over 20MB, it will be rejected as long as you are a member of this distribution group.