All of the sudden, when a user receives an email from another internal email user, they immediately receive another email with the original email as an attachment that says it is from 'MICROSOFT OUTLOOK on behalf of Sender of message'
Just seems to be one user. I've verified that there are no send as permissions. No rules. The auto relay in the delivery options is unset.
This does not happen when an external domain message is received but does happen when the user sends a message both internally and externally.
We are using exchange 2010. And I am testing using OWA to rule out any client issues.