sendEmail: 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/lib/prey/platform/linux/bin/sendEmail - from package: prey
/usr/bin/sendemail - from package: sendemail

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

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