doveadm: 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/doveadm - from package: dovecot

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

On Debian possible default full paths are:

/usr/bin/doveadm - from package: dovecot-core

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

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