aliases(4) (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, which is invoked
automatically by sendmail, maintains these files.
~/.forward Addresses to which a user's mail is forwarded
(see Automatic Forwarding, below).
In addition, the YP name services 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.
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DARPA-standard Addresses
username@domain
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:
.COM Commerical organizations.
.EDU Educational organizations.
.GOV Government organizations.
.MIL 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.
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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:
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.
YP Domain Aliases
Normally, the aliases file on the master YP server is used for the
mail.aliases YP map, which can be made available to every YP 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 YP client could just mail to jsmith and not have to remember
the machine and username for John Smith. If a YP alias does not
resolve to an address with a specific host, then the name of the YP
domain is used. There should be an alias of the domain name for a
host in this case. For example, the alias:
jsmith:root
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sends mail on a YP client to root@podunk-u if the name of the YP
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 YP aliases. Otherwise, copies of the message may ``bounce.''
Usually, the solution is to change the YP alias to direct mail to the
proper destination.
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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