I have followed this guide.
It looks like everything is working except for this last error.
Outlook express -
Error message from the client:
There was a problem logging onto your mail server. Your Password was rejected. Account: '192.168.81.120', Server: '192.168.81.120', Protocol: POP3, Server Response: '-ERR chdir example.com/sales/ failed', Port: 110, Secure(SSL): No, Server Error: 0x800CCC90, Error Number: 0x800CCC92
I can confirm that creating the directory /home/vmail/example.com/sales/ removes this error message but cannot send or receive mail.
I must have made a mistake somewhere why isn't it creating the directory on its own.