Your users with FTP and/or shell access can create their own mail forwarding files so that mail that would otherwise be delivered to their user account can be redirected to any address or addresses they wish. This feature frees you from the administrative task of managing user aliases, and allows your users the ability to create or modify their own alias without having to wait on you to do it for them.
A user’s mail forwarding file must be placed in their home directory, and must have the name .forward in order to work properly. This file should contain one or more valid email addresses separated by commas, as in the following example:
dave@somedomain.com, mike@someotherdomain.com
Additionally, the file must be owned by the user and not be writable to anyone else or the mail forwarding for the user will not work.