There are three ways to change an e-mail account's password.
Log into the web UI of Vesta as the user the domain is hosted in and change the password.
It is also possible to call vesta's scripts under
v-change-mail-account-password USER DOMAIN ACCOUNT PASSWORD
password plug-in for roundcube is enabled and set to the
vesta driver, you can also reset the password by logging in to the werbmail, and selecting "Password" in the settings. For this to work, you'll have to make sure the driver exists in
plugins/password/drivers/vesta.php. Be reminded that Vesta comes with a driver preconfigured under