unmime.gz: 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/share/doc/mailagent/examples/rc/sbin/unmime.gz - from package: mailagent

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

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