imtest: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/imtest - from package: cyrus-imapd-utils

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/imtest - from package: cyrus-clients

You may install the required package with command apt-get install {package}

Error in other languages:
imtest: bevel nie gevind nie
imtest: comandă negăsită
imtest: comando não encontrado
imtest: commande introuvable
imtest: command not found
imtest: käsku ei ole
imtest: không tìm thấy lệnh
imtest: komanda nerasta
imtest: Kommando nicht gefunden.
imtest: kommandot finns inte
imtest: komut yok
imtest: nie znaleziono polecenia
imtest: níor aimsíodh an t-ordú
imtest: no se encontró la orden
imtest: no s'ha trobat l'ordre
imtest: opdracht niet gevonden
imtest: parancs nem található
imtest: perintah tidak ditemukan
imtest: príkaz nenájdený
imtest: příkaz nenalezen
imtest: команда не найдена
imtest: командата не е открита
imtest: 命令找不到
imtest: コマンドが見つかりません