All users in a local domain can use the entries that are in the NIS aliases map. The reason is that the sendmail program can use the NIS aliases map instead of the local /etc/mail/aliases files to determine mailing addresses. For more information, refer to the nsswitch.conf(4) man page.
Aliases in the NIS aliases map adhere to the following format.
aliasname: value,value,value ...
aliasname is the name that the user uses when sending mail, and value is a valid email address.
The NIS aliases map should contain entries for all mail clients. In general, only the root user on the NIS master can change these entries. This type of alias might not be a good choice for aliases that are constantly changing. However, such aliases can be useful if the aliases point to another alias file, as in the following syntax example.
aliasname is the name that the user uses when sending mail, and host is the host name for the server that contains an /etc/mail/alias file.