I have 2 e-mail servers running in my office that are taking care of 2 different domains. One server is running send mail and the other server is running Zimbra. The username firstname.lastname@example.org and email@example.com exist.
When I try and send a message to firstname.lastname@example.org from the zimbra server I get a user unknown message from Postfix. This makes no sense and any help is appreciated!