how do i send an email through joomla

I have a system so folks can register for a class through my Joomla site (I believe it's 3.0). But from there, I would like to send folks an email filling variables from the registration. So something like:

Dear (name), thank you for registering for (class). 
This is to remind you your class is tomorrow, (date), at (place).

I believe for the registration, the system uses authorize.net

How can I accomplish this?

Thanks for the help!!