sendxmpp: 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 CentOS possible default full paths are:

/usr/bin/sendxmpp - from package: sendxmpp

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/sendxmpp - from package: sendxmpp

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

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