geary-attach: 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 Debian possible default full paths are:

/usr/bin/geary-attach - from package: geary

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

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