I have email server external which is hosting my domain emails. I want to setup an internal server so that certain people can get their emails downloaded from internal server and the people who work on remote sites can get their emails from external server. My external server will have a catch all account and it will drop all the emails to my internal Mdaemon mail server. they both use the same domain name. I have set it up and it works fine but when internal users send emails to external users it gives error that their email address in not correct. The error comes because the internal server cannot see the external server email addresses of the remote users. How can I solve this issue.