I have a problem with external meeting notices. When one of my users sends a notice out the network, the organizer field uses the SMTP address - which in my system is the users mailbox, server, and domain name. We convert this user name to first.m.last@xxxxxxxxxx when messages go out (visa versa when they come in). This conversion is done on our gateway server (non-Microsoft server). External meeting replies are being bounced because the return address (organizer field) is not a valid user address. Does anyone know how to modify the organizer field? Because of my environment, there's not the option to change the SMTP address in Exchange. I have to find a solution for modifying the organizer field.