The system has not been configured to send emails. Go to SMTP settings or ask your administrator to set them
First of all you need to have a set host. You need to check if your settings are correct - if you use a different SMTP port (other than 25) try and see that you can actually have permissions to connect to this server on this port.
In order for the forgot password form to be working correctly you need to set the following values in your membership provider:
Also, for recoveryMailBody you need to use the following special tags somewhere in the mail body:
Otherwise the system won't be able to send proper emails.