Topic: installation failed
root@mail:/home/silent/Downloads/iRedMail-0.6.1/pkgs# bash get_all.sh
< INFO > Creating necessary directories ...
< INFO > ==================== Fetching Source Tarballs ====================
< INFO > * 1/5: http://iredmail.org/apt/misc/postfixadmin_2.3.tar.gz
< INFO > * 2/5: http://iredmail.org/apt/misc/iRedAdmin-0.1.3.tar.bz2
< INFO > * 3/5: http://iredmail.org/apt/misc/iRedAPD-1.3.3.tar.bz2
< INFO > * 4/5: http://iredmail.org/apt/misc/roundcubemail-0.3.1.tar.gz
< INFO > * 5/5: http://iredmail.org/apt/misc/phpldapadmin-184.108.40.206.tgz
< INFO > Validate Packages ... [ OK ]
< INFO > Checking necessary command/package: dialog/dialog ...
< INFO > Installing package(s): dialog
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package dialog is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'dialog' has no installation candidate
< ERROR > Installation failed, please check the terminal output
plis somebody to help me...thanks in advance