sup-recover-sources: 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/sup-recover-sources - from package: sup-mail

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