You see the following error in your mail log:
Feb 24 21:42:39 mail postfix/trivial-rewrite: warning: do not list domain example.com in BOTH mydestination and virtual_mailbox_domains
You have example.com in the resource (for example a MySQL database) referenced in the virtual_mailbox_domains directive in /etc/postfix/main.cf AND in the mydestination line (also in /etc/postfix/main.cf)! This doesn’t work. You can list example.com either in virtual_mailbox_domains or in mydestination, but not in both.
Please correct this and restart Postfix: