I'm having issues in a migration environment. I am moving mailboxes from 2010 to 2013 and I'm having issues reaching outlook externally. I have rpc over http all setup and the mailbox passes all checks on testconnectivity.com. But when I am external from the network I get the error "The action cannot be completed. The name cannot be matched to a name in the address list. I verified there are no weird MDB entries in ADSI edit so I'm not sure why this is an issue.