I'm attempting to replace a failing Exchange Server. Had one configured from a few years ago, launched it, migrated mailboxes and everything seems find within our domain (send-receive) and will send outbound but will not receive from out of domain. have 4 different offices on t-1 connection through AT&T cloud. I've never worked with Exchange so any advise or pointers to implementation guides would be appreciated. Working on third day with no sleep. HELP!!