These are the contents of '/etc/aliases' file on my Debian (Wheezy) server, as it is:
# /etc/aliases
mailer-daemon: postmaster
postmaster: root
nobody: root
hostmaster: root
usenet: root
news: root
webmaster: root
www: root
ftp: root
abuse: root
noc: root
security: root
root: t
1. I noticed that, by default, my server sends email from what looks like root@hostname.domain.com
. So, which one of the rules above governs this? postmaster: root;
?
2. So, the rules in '/etc/aliases' are used to assign users to specific departments? That is, for example, all emails to be sent/received for 'abuse' will be delivered from/to root@hostname.domain.com (which'd be the default email for root, unless there's an alias). Correct?
3. Can someone please explain what each of these really meant for — mailer-daemon, postmaster, nobody, hostmaster, usenet, news, webmaster, www, ftp, abuse, noc, security, root?
I mean, a description like "mailer-daemon
for sending email delivery errors, but not really meant for receiving emails. security
for where people should contact your about security issues", or something like that.
Best Answer
The
/etc/aliases
file is part ofsendmail
. It specifies which account mail sent to an alias should really be delivered to. For example, mail to theftp
account would be sent to root's mailbox in the configuration you show.Multiple recipients can be specified as comma-separated lists, too.
Redirecting mail to users isn't all that can be done. Mail can be piped to programs, too, or simply directed into a file of your choice. The following would "bit-bucket" all mail from the user "somebody":
somebody : /dev/null
Modifications to the
/etc/aliases
file are not complete until thenewaliases
command is run to build/etc/aliases.db
. It is in this later form thatsendmail
actually uses.