> If the probe guesses wrong, an error is raised rather than
> an "email has been sent" message.
>
> In this case I would suggest disabling the reset mechanism
> entirely (although I am not quite sure how this would be done).

To do this just replace the passrst action using an extension.

The extension wraps the existing actions.PassResetAction to see if
the user email exists. If not return a "Email sent to $address"
using the submitted address but don't actually send anything. If
the email is valid call actions.PassResetAction to do the reset.

See how the login action is wrapped in: https://wiki.roundup-
tracker.org/LoginWithEmail

Added documentation on how password reset works in the web interface
rev:6257:f9c059921ccc