mimesend: 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/mimesend - from package: perl-MIME-tools

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

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