imapd-ssl: 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/imapd-ssl - from package: courier-imap-ssl

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

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