Hi,

Yes; the Maildir mail boxes are created by Postfix, on delivery of mail. As long as /var/mail/vmail is writable by postfix, you'll be fine.

If the mailbox doesn't exist you may experience problems with the IMAP/POP3 server giving an error message when the end user attempts to login. For this reason, it's normally a good idea to send a "welcome" message upon creation of the mailbox.