imap4d: 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 Debian possible default full paths are:

/usr/sbin/imap4d - from package: mailutils-imap4d

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

Error in other languages:
imap4d: bevel nie gevind nie
imap4d: comandă negăsită
imap4d: comando não encontrado
imap4d: commande introuvable
imap4d: command not found
imap4d: käsku ei ole
imap4d: không tìm thấy lệnh
imap4d: komanda nerasta
imap4d: Kommando nicht gefunden.
imap4d: kommandot finns inte
imap4d: komut yok
imap4d: nie znaleziono polecenia
imap4d: níor aimsíodh an t-ordú
imap4d: no se encontró la orden
imap4d: no s'ha trobat l'ordre
imap4d: opdracht niet gevonden
imap4d: parancs nem található
imap4d: perintah tidak ditemukan
imap4d: príkaz nenájdený
imap4d: příkaz nenalezen
imap4d: команда не найдена
imap4d: командата не е открита
imap4d: 命令找不到
imap4d: コマンドが見つかりません