425202 Mantis Expert needed to Config

I have mantis bug traker intsalled on my server but the SMTP ie the mail fuctionality is not working need it configured properely So the when a bug is assigned the person the bug is assigned get the email also the ability to reset email This is urgent Please only respond if you are familiar and can do this Thanks One more thing I already have bugs entered into the system and do not want to lose the data thanks