OnWorks favicon

aliascheck - Online in the Cloud

Run aliascheck in OnWorks free hosting provider over Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator

This is the command aliascheck that can be run in the OnWorks free hosting provider using one of our multiple free online workstations such as Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator



aliascheck - check for existence of mail alias


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

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

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


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

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.


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
# Fall through to default checks
reject unknown user
# Probably safest to do nothing, but could also
# defer the mail with the following command:
#defer Temporary error processing alias file

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

Use aliascheck online using onworks.net services

Free Servers & Workstations

Download Windows & Linux apps

  • 1
    Eclipse Tomcat Plugin
    Eclipse Tomcat Plugin
    The Eclipse Tomcat Plugin provides
    simple integration of a tomcat servlet
    container for the development of java
    web applications. You can join us for
    Download Eclipse Tomcat Plugin
  • 2
    WebTorrent Desktop
    WebTorrent Desktop
    WebTorrent Desktop is for streaming
    torrents on Mac, Windows or Linux. It
    connects to both BitTorrent and
    WebTorrent peers. Now there's no
    need to wait for...
    Download WebTorrent Desktop
  • 3
    GenX is a scientific program to refine
    x-ray refelcetivity, neutron
    reflectivity and surface x-ray
    diffraction data using the differential
    evolution algorithm....
    Download GenX
  • 4
    PSPP is a program for statistical
    analysis of sampled data. It is a free
    replacement for the proprietary program
    SPSS. PSPP has both text-based and
    graphical us...
    Download pspp4windows
  • 5
    Git Extensions
    Git Extensions
    Git Extensions is a standalone UI tool
    for managing Git repositories. It also
    integrates with Windows Explorer and
    Microsoft Visual Studio
    (2015/2017/2019). Th...
    Download Git Extensions
  • 6
    This is an application that can also be
    fetched from
    It has been hosted in OnWorks in order
    to be run online in an easi...
    Download jtdx
  • 7
    eSpeak: speech synthesis
    eSpeak: speech synthesis
    Text to Speech engine for English and
    many other languages. Compact size with
    clear but artificial pronunciation.
    Available as a command-line program with
    many ...
    Download eSpeak: speech synthesis
  • More »

Linux commands