sendfiles: command not found

Have You tried accessing the binary with the full path?

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

[root@server ~]# echo $PATH

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/bin/mh/sendfiles - from package: nmh

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