Currently I have virtual users defined and the mail location is set as:

mail_location = maildir:/var/mail/vhosts/%d/%n

This works fine for my virtual users. However my local Linux users mail is not getting to their mailbox and the error message in the log looks like:

User doesn't exist: james@saturn.myserver.com

The mail location for this user is located at /var/mail/james

My guess is that the mail_location setting above takes precedence. I think I'm supposed to use namespace to configure this but this namespace thing is something new to me and I don't know how to begin, to configure a namespace for both the virtual users and the local unix/linux users. Any example is greatly appreciated. Thanks.