rxtelnet: 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/bin/rxtelnet - from package: heimdal-clients-x

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

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