Office 365
There are a couple of methods for setting up the response for test messages. There are some significant differences in how the response works and those methods are outlined here.
Setting the forward on the contact.
Screen shots and step by step instructions Method 1
Forwarding the message through the contact will retain all header information for the receiving and returing the message. However, on the return path if there is third-part filtering/scanning this method has been known to bypass these and instead sends the message back to Knowledge Front from the Microsoft servers.
Using a mailbox with a rule for the response
Screen shots and step by step instructions Method 2
Using a rule to respond to test messages will cause the envelope to be created new at the point the rule triggers. This loses all header information created during delivery of the test message. Only the outboud headers (returning to Knowledge Front) will remain. If there are backend services being tested sometimes this is the only method available that will follow the exact path of a normal email.