Using the --newuser command fails to do two things to make a changed account a functional email account when switching from user.account postfix style to email@example.com style.
It doesn't add a user-domain style user to /etc/passwd It doesn't correctly then enter the alias in /etc/postfix/virtual
it enters: firstname.lastname@example.org user\@example.com
It should enter: email@example.com user-example.com
Background: I was using the --newuser function to changeaccounts to an alternate name and then back to update them to the firstname.lastname@example.org style that was changed in the template after initial virtual domain and mail account creation.
More info in the thread here: https://www.virtualmin.com/node/15708#comment-68932