imapd: 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/sbin/imapd - from package: uw-imap

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

On Debian possible default full paths are:

/usr/sbin/imapd - from package: courier-imap
/usr/bin/imapd - from package: courier-imap
/usr/lib/cyrus/bin/imapd - from package: cyrus-imapd

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

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