Dec 6 12:30:52 ubuntuer postfix/trivial-rewrite: warning: do not list domain lewendewoord.co.za in BOTH mydestination and virtual_mailbox_domains
This line is one of the culprits, I have had the same problem for last day or two just fixed it now.
in /etc/postfix/main.cf you probably have
mydestination = lewendewoord.co.za, localhost, localhost.localdomain
change this to
mydestination = SERVERNAME , localhost, localhost.localdomain
so if your server is called myserver then insert myserver where SERVERNAME is.