installto.sh: 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/share/roundcubemail/bin/installto.sh - from package: roundcubemail

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

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