aliases(4) UNIX System V(BSD Compatibility Package) aliases(4)
NAME
aliases, addresses, forward - addresses and aliases for sendmail
SYNOPSIS
/etc/aliases
/etc/aliases.dir
/etc/aliases.pag
~/.forward
DESCRIPTION
These files contain mail addresses or aliases, recognized by sendmail,
for the local host:
/etc/passwd Mail addresses (usernames) of local users.
/etc/aliases Aliases for the local host, in ASCII format. This
file can be edited to add, update, or delete local
mail aliases.
/etc/aliases. { dir , pag}
The aliasing information from /etc/aliases, in
binary, dbm format for use by sendmail. The program,
newaliases, maintains these files.
~/.forward Addresses to which a user's mail is forwarded (see
Automatic Forwarding, below).
In addition, the Network Information Service (NIS) aliases map
mail.aliases contains addresses and aliases available for use across the
network.
Addresses
As distributed, sendmail supports the following types of addresses:
Local Usernames
username
Each local username is listed in the local host's /etc/passwd file.
Local Filenames
pathname
Messages addressed to the absolute pathname of a file are appended to
that file.
Commands
|command
If the first character of the address is a vertical bar, (|), sendmail
pipes the message to the standard input of the command the bar precedes.
DARPA-standard Addresses
username@domain
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If domain does not contain any `.' (dots), then it is interpreted as the
name of a host in the current domain. Otherwise, the message is passed
to a mailhost that determines how to get to the specified domain.
Domains are divided into subdomains separated by dots, with the top-level
domain on the right. Top-level domains include:
Commerical organizations.
Educational organizations.
Government organizations.
Military organizations.
For example, the full address of John Smith could be:
js@jsmachine.Podunk-U.EDU
if he uses the machine named jsmachine at Podunk University.
uucp Addresses
... [host!]host!username
These are sometimes mistakenly referred to as ``Usenet'' addresses. uucp
provides links to numerous sites throughout the world for the remote
copying of files.
Other site-specific forms of addressing can be added by customizing the
sendmail configuration file. See the sendmail(1M) for details. Standard
addresses are recommended.
Aliases
Local Aliases
/etc/aliases is formatted as a series of lines of the form
aliasname:address[, address]
aliasname is the name of the alias or alias group, and address is the
address of a recipient in the group. Aliases can be nested. That is, an
address can be the name of another alias group. Because of the way
sendmail performs mapping from upper-case to lower-case, an address that
is the name of another alias group must not contain any upper-case
letters.
Lines beginning with white space are treated as continuation lines for
the preceding alias. Lines beginning with # are comments.
Special Aliases
An alias of the form:
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owner- aliasname : address
directs error-messages resulting from mail to aliasname to address,
instead of back to the person who sent the message.
An alias of the form:
aliasname: :include:pathname
with colons as shown, adds the recipients listed in the file pathname to
the aliasname alias. This allows a private list to be maintained
separately from the aliases file.
NIS Domain Aliases
Normally, the aliases file on the master NIS server is used for the
mail.aliases NIS map, which can be made available to every NIS client.
Thus, the /etc/aliases* files on the various hosts in a network will one
day be obsolete. Domain-wide
aliases should ultimately be resolved into usernames on specific hosts.
For example, if the following were in the domain-wide alias file:
jsmith:js@jsmachine
then any NIS client could just mail to jsmith and not have to remember
the machine and username for John Smith. If a NIS alias does not resolve
to an address with a specific host, then the name of the NIS domain is
used. There should be an alias of the domain name for a host in this
case. For example, the alias:
jsmith:root
sends mail on a NIS client to root@podunk-u if the name of the NIS domain
is podunk-u.
Automatic Forwarding
When an alias (or address) is resolved to the name of a user on the local
host, sendmail checks for a file, owned by the intended recipient, in
that user's home directory, and with universal read access. This file
can contain one or more addresses or aliases as described above, each of
which is sent a copy of the user's mail.
Care must be taken to avoid creating addressing loops in the file. When
forwarding mail between machines, be sure that the destination machine
does not return the mail to the sender through the operation of any NIS
aliases. Otherwise, copies of the message may ``bounce.'' Usually, the
solution is to change the NIS alias to direct mail to the proper
destination.
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A backslash before a username inhibits further aliasing. For instance,
to invoke the vacation program, user js creates a file that contains the
line:
\js, "|/usr/ucb/vacation js"
so that one copy of the message is sent to the user, and another is piped
into the vacation program.
FILES
/etc/passwd
/etc/aliases
~/.forward
SEE ALSO
newaliases(1M), sendmail(1M), vacation(1), dbm(3X)
uucp(1C), in the User's Reference Manual
NOTES
Because of restrictions in dbm a single alias cannot contain more than
about 1000 characters. Nested aliases can be used to circumvent this
limit.
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