Get the bounced mail which are not present in virutal mail box

There may be time when you would like to grab bounced mails from the logs which you might have given to someone but forgot to create as --add-mailalias in YunoHost.
In other words if the mail gets bounced because the email id in not linked to any account, you can grab them by this command:

$ grep 'User unknown in virtual mailbox table' /var/log/mail.log | sed -e 's/.*to=<//g' | sed -e 's/>.*//g' | sort -t: -u -k1,1

This is important if you are missing some mails because you thought that mail is registered to your server but actually its not.