We are 90% there, but having issues with a simple piece that is causing issues. We can receive emails sent to a test mailbox on Exc 2013 server from both internal 2007 users and external users. We can also send to external user, but not to internal 2007 users. It appears to get caught up on with ether the 2013 Send connector or the 2007 receive connector. Not sure how to trouble shoot this or look at logs to determine error location.