mailshar: 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/mailshar - from package: sharutils

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

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