exchange2ical: 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/exchange2ical - from package: openchange-client

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

On Debian possible default full paths are:

/usr/bin/exchange2ical - from package: openchangeclient

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

Error in other languages:
exchange2ical: bevel nie gevind nie
exchange2ical: comandă negăsită
exchange2ical: comando não encontrado
exchange2ical: commande introuvable
exchange2ical: command not found
exchange2ical: käsku ei ole
exchange2ical: không tìm thấy lệnh
exchange2ical: komanda nerasta
exchange2ical: Kommando nicht gefunden.
exchange2ical: kommandot finns inte
exchange2ical: komut yok
exchange2ical: nie znaleziono polecenia
exchange2ical: níor aimsíodh an t-ordú
exchange2ical: no se encontró la orden
exchange2ical: no s'ha trobat l'ordre
exchange2ical: opdracht niet gevonden
exchange2ical: parancs nem található
exchange2ical: perintah tidak ditemukan
exchange2ical: príkaz nenájdený
exchange2ical: příkaz nenalezen
exchange2ical: команда не найдена
exchange2ical: командата не е открита
exchange2ical: 命令找不到
exchange2ical: コマンドが見つかりません