554 5.6.0 Invalid content when sending to internal Exchange Server

Resolution:

• If you are using a third party scanning plugin on the Exchange server, check the configuration of the plugin.
• It may be useful to exclude the MailMarshal server from Exchange Sender ID and Connection Filtering. You can do this by editing the Transport Settings:
  1. In Exchange Management Console, navigate to Organization Configuration > Hub Transport > Global Settings tab.
     
     
     
     
      
  2. Double-click the Transport Settings item and select the Message Delivery tab.
     
     
  3. Add the IP address of the MailMarshal server to the list.
  4. Save changes.