Newaliases rebuilds the random access data base for the mail aliases file /etc/aliases. It must be run each time this file is changed in order for the change to take effect.
Newaliases is identical to “sendmail -bi”.
The newaliases utility exits 0 on success, and >0 if an error occurs.
Notice: do not use makemap to create the aliases data base, because newaliases puts a special token into the data base that is required by sendmail.
The mail aliases file
The newaliases command appeared in 4.0BSD.