pyami_sendmail: 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/pyami_sendmail - from package: python2-boto
/usr/bin/pyami_sendmail - from package: python-boto

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

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