When using the "Reason: Failure sending mail" option in Helm and you receive the error "An exception occurs while sending the email out, please contact your administrator. Reason: Failure sending mail." this is most likely caused by the mail server not relaying mail for the local IP address without authentication.
To resolve the problem in SmarterMail login as the admin user.
Select "Security" and then "SMTP Authentication Bypass" - then using the "Add IP Address(s)" option add the external IP address of the server to the allowed to relay list.
You should now be able to recover passwords via the Helm login page.