aliascheck - Online in the Cloud

PROGRAM:

NAME

aliascheck - check for existence of mail alias

SYNOPSIS

aliascheck [--nopwd] name [alias-file]

aliascheck --map [--case] name map-file

aliascheck --qmail [--nopwd] name [alias-user]

DESCRIPTION

aliascheck checks whether name is a valid email alias or a user in the password file. It
converts name to lower-case before performing any of the checks. If the alias or user
exists, aliascheck exits with status 0 and outputs what the address resolves to. If the
alias does not exist, aliascheck exits with status 1. If aliascheck cannot determine the
validity of name because of some system error, it exits with status 2.

aliascheck can run in three different modes--sendmail alias mode (the default), sendmail
map mode, and qmail mode. In sendmail alias mode the second argument, alias-file, is the
name of the sendmail alias file, typically /etc/mail/aliases.db. If no second argument is
supplied, aliascheck first checks for the existence of /etc/mail/aliases.db, then for the
existence of /etc/aliases.db, then finally exits with status 2 if neither file exists.
When an alias is found, aliascheck outputs the value of that alias in the alias database.

When aliascheck is invoked with --map, it looks up name in map-file, which should be a
database created with sendmail's makemap(8) utility. Note that maps have a slightly
different and incompatible format from that of alias files. Use the --case argument to
prevent name from being folded to lower-case before it is looked up in the database. Note
that --map implies the --nopwd option.

When aliascheck is given the argument --qmail, it runs in qmail mode. In this case, the
second argument, alias-user, specifies the user under which qmail processes mail aliases.
aliascheck will check this user's home directory for files named .qmail-XXX for various
appropriate suffixes XXX. On success, it outputs the full pathname of the appropriate
file.

If aliascheck cannot find an alias, it also checks the password file, and exits 0 if it
can find name there. If name is found, aliascheck also outputs name (in lower-case) to
standard output before exiting. (This is useful for Mail Avenger, because asmtpd does not
recognize users with invalid shells or UID 0, while MTAs typically do.) To suppress
password file checking, supply the --nopwd argument to aliascheck.

EXAMPLES

If you are using Mail Avenger in conjunction with a sendmail installation, you might want
to put the following code in your /etc/avenger/unknown file to reject mail for unknown
users who do not show up in the alias file.

aliascheck "$RECIPIENT_LOCAL" /etc/mail/aliases.db > /dev/null
case "$?" in
0)
# Fall through to default checks
;;
1)
reject unknown user
;;
*)
# Probably safest to do nothing, but could also
# defer the mail with the following command:
#
#defer Temporary error processing alias file
;;
esac

If you have qmail instead of sendmail, assuming the qmail alias user is called "alias",
you would change the first line in the previous example to:

aliascheck --qmail "$RECIPIENT_LOCAL" alias > /dev/null

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