To be able to store the received e-mail in the correct mailbox for your users you have to setup a location that you will use on your servers harddisk. A very common location is ‘/usr/local/virtual’, but you can put it anywhere you want. Keep in mind that if you use a different location that you need to change several configuration files (I’ll try to put remarks on this at the proper locations)
If you are installing for the first time the directory isn’t there yet. You need to create it and setup the correct permissions. So login to a Terminal session of your server and execute the following commands or use the shell script provided at the bottom of this page.
First create the required directory:
sudo mkdir /usr/local/virtual
Change the owner and group of the directory to be postfix so that the postfix program can read and write into that directory:
sudo chown -R postfix:postfix /usr/local/virtual
and setup the correct permissions
sudo chmod 771 /usr/local/virtual