smtptest: 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/smtptest - from package: cyrus-imapd-utils

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

On Debian possible default full paths are:

/usr/bin/smtptest - from package: cyrus-clients

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

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