Da Voismart Knowledge Base.
Authenticate with Voicemail passwords

  VMAuthenticate([mailbox][@context][|options]): This application behaves the
same way as the Authenticate application, but the passwords are taken from
  If the mailbox is specified, only that mailbox's password will be considered
valid. If the mailbox is not specified, the channel variable AUTH_MAILBOX will
be set with the authenticated mailbox.

    s - Skip playing the initial prompts.