rcvtty.fixup: 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/mh-book/examples/mh/bin/rcvtty.fixup - from package: mh-book

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

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