If someone change aliases for user with alias defined earlier, then he would get a several lines for single user in aliases file. Only one line per user is valid, if you have more, then you will get something like this in postfix logs:
Jun 18 22:28:47 admin postfix/postalias[14529]: warning: /etc/aliases.db: duplicate entry: "root"
If someone change aliases for user with alias defined earlier, then he would get a several lines for single user in aliases file. Only one line per user is valid, if you have more, then you will get something like this in postfix logs:
Jun 18 22:28:47 admin postfix/postalias[14529]: warning: /etc/aliases.db: duplicate entry: "root"